Moving picture encoding device, moving picture encoding method and moving picture encoding program, and moving picture decoding device, moving picture decoding method and moving picture decoding program

ABSTRACT

In inter prediction that is performed by partitioning a first block, which is obtained by partitioning each picture, into one or more second blocks, a spatial merge candidate generating unit derives a spatial merge candidate without referring to a block included in a first block that includes a second block. In case of a mode where a coding block is divided by a horizontal border into prediction blocks arranged vertically, the reference index derivation unit of a time merge candidate sets reference index information of a time merge candidate to a value of reference index information of an encoded prediction block adjacent to a left edge of a prediction block subject to encoding.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. patent application Ser. No.14/298,635, filed Jun. 6, 2014, which is a Continuation of PCTInternational Application No. PCT/JP2012/008016, filed Dec. 14, 2012,which claims the benefit of Japanese Patent Application Nos.2011-276456, filed Dec. 16, 2011, and 2011-289287 and 2011-289288, filedDec. 28, 2011, and 2011-276457, filed Dec. 16, 2011, and 2012-273314 and2012-273315, filed Dec. 14, 2012.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a moving picture encoding anddecoding technology, and more particularly, to a moving picture encodingand decoding technology utilizing motion compensation prediction.

2. Description of the Related Art

As a typical moving picture compression-coding method, there is MPEG-4AVC/H.264 standard. The MPEG-4 AVC/H.264 utilizes motion compensation,where a picture is partitioned into a plurality of rectangular blocks, apicture that has been already encoded or decoded is used as a referencepicture, and a movement from the reference picture is predicted. Amethod that predicts movement by this motion compensation is referred toas inter prediction or motion compensation prediction. According tointer prediction of MPEG-4AVC/H.264, a plurality of pictures can be usedas reference pictures, and a most appropriate reference picture ischosen from the plurality of reference pictures for each block so as toperform motion compensation prediction. Therefore, a reference index isassigned to each reference picture, and a reference picture is specifiedby the reference index. For a B picture, up to two pictures can beselected from decoded reference pictures and be used for interprediction. Two types of prediction based respectively on these tworeference pictures are distinguished as L0 prediction (list 0prediction), which is mainly used as prediction for a previous picture,and L1 prediction (list 0 prediction), which is mainly used asprediction for a subsequent picture, respectively.

In addition, bi-prediction, which uses two types of inter prediction(i.e., L0 prediction and L1 prediction), is also defined. In case ofbi-prediction, prediction for both directions is performed,inter-predicted signals of L0 prediction and L1 prediction respectivelyare multiplied by a weighting coefficient, an offset value is added andconvolution is performed so as to generate an ultimate inter predictionpicture signal. The weighting coefficient used for weighted predictionand the offset value are defined by a typical value for each referencepicture of each list on a picture by picture basis, and encoded. Codinginformation relating to inter prediction includes: a prediction modethat differentiate among L0 prediction, L1 prediction, and bi-predictionfor each block; a reference index that specifies a reference picture foreach reference list of each block; and a motion vector that represents adirection of movement and an amount of movement of a block. This codinginformation is encoded and/or decoded.

Further, according to MPEG-4 AVC/H.264, a direct mode, where interprediction information of a block subject to encoding or decoding isgenerated from inter prediction information of a decoded block, isdefined. Since encoding of inter prediction information is not required,encoding efficiency is improved with the direct mode.

An explanation will be given on a time direct mode that uses acorrelation of inter prediction information over time, while referringto FIG. 42. A picture, of which the reference index of L1 is registeredto 0, is used as a base picture colPic. A block at a position identicalto a block subject to encoding or decoding in the base picture colPic isused as a base block.

If the base block is encoded by using L0 prediction, the motion vectorof the base block L0 is used as a base motion vector mvCol. If the baseblock is not encoded by using L0 prediction but encoded by using L1prediction, the motion vector of L1 of the base block is used as a basemotion vector mvCol. A picture referred to by the base motion vectormvCol is used as a reference picture of L0 in a time direct mode, andthe base picture colPic is used as a reference picture of L1 in a timedirect mode.

A motion vector mvL0 of L0 and a motion vector mvL1 of L1 in a timedirect mode are derived from a base motion vector mvCol by a scalingcomputation process.

By subtracting POC of the reference picture of L0 in a time direct modefrom POC of the base picture colPic, a distance td between pictures isderived. POC is defined as a parameter that is associated with a picturesubject to encoding, and a value that increases in the output order ofpictures is set. A difference of POC between two pictures indicates adistance between pictures along the time axis.

td=POC of a base picture colPic−POC of a reference picture of L0 in atime direct mode

By subtracting POC of the reference picture of L0 in a time direct modefrom POC of a picture subject to encoding or decoding, a distance tbbetween pictures is derived.

tb=POC of a picture subject to encoding or decoding−POC of a referencepicture of L0 in a time direct mode

A motion vector mvL0 of L0 in a time direct mode is derived from a basemotion vector mvCol by a scaling computation process.

mvL0=tb/td*mvCol

A motion vector mvL1 of L1 is derived by subtracting the base motionvector mvCol from the motion vector mvL0 of L0 in a time direct mode.

mvL1=mvL0−mvCol

RELATED ART LIST Patent Document

[Patent Document1] Japanese Patent Application Publication No.2004-129191.

SUMMARY OF THE INVENTION

However, in accordance with the conventional method, for a block subjectto encoding and a block subject to decoding, in some cases, the degreeof prediction accuracy is decreased and the encoding efficiency is notimproved with a time direct mode.

In this background, the present inventors have recognized the necessityof further compression of coding information and reduction of the totalamount of code in a moving picture encoding method that uses motioncompensation prediction.

SUMMARY OF THE INVENTION

The present invention addresses the aforementioned issue, and a purposethereof is to provide a moving picture encoding and decoding technologyfor reducing an amount of code of coding information by calculating acandidate of coding information, so as to improve the encodingefficiency.

In order to address the aforementioned issue, a moving picture encodingdevice is provided according to an aspect of the present invention. Thedevice partitions a first block, which is obtained by partitioning eachpicture, into one or more second blocks and encodes a moving pictureusing inter prediction. The device includes: a first predictioninformation derivation unit (130) configured to derive a first interprediction information candidate from inter prediction information of athird block in a proximity of the second block subject to encoding in apicture subject to encoding; a second prediction information derivationunit (132) configured to derive a second inter prediction informationcandidate from inter prediction information of a fourth block at aposition identical to or in a proximity of the second block subject toencoding in a picture different from the picture subject to encoding; acandidate list construction unit (133) configured to construct aprediction information candidate list including a prediction informationcandidate to which, in case that the first inter prediction informationcandidate is derived, the derived first inter prediction informationcandidate is added, and in case that the second inter predictioninformation candidate is derived, the derived second inter predictioninformation candidate is added, respectively; a selection unit (136)configured to select a candidate of inter prediction information to beused for the inter prediction of the second block subject to encodingfrom the one or more prediction information candidates in the predictioninformation candidate list, and configured to determine an indexindicating inter prediction information; an encoding unit (110)configured to encode the index indicating inter prediction informationto be used for the inter prediction of the second block subject toencoding. The first prediction information derivation unit (130) doesnot use, as the first inter prediction information candidate, codinginformation of a fifth block included in a block identical to the firstblock including the second block subject to encoding.

According to another aspect of the present invention, also a movingpicture encoding device is provided. The device partitions a codingblock into one or more prediction blocks in accordance with a partitionmode so as to perform motion compensation prediction. The deviceincludes: a reference index derivation unit (131) configure to derive,in a merge mode where inter prediction information defined as a timemerge candidate is derived from inter prediction information of aprediction block at a position identical to or in a proximity of aprediction block subject to encoding in a encoded picture different intime from the prediction block subject to encoding and inter predictionof the prediction block subject to encoding is executed on the basis ofthe derived inter prediction information, reference index information ofa time merge candidate as reference index information that specifies areference picture used in the prediction block subject to encoding; anda time merge candidate generating unit (132) configured to derive interprediction information of time merge candidate based on the derivedreference index information. In case that the partition mode is a modewhere the coding block is divided by a horizontal border into predictionblocks arranged vertically, the reference index derivation unit (131)sets reference index information of a time merge candidate to a value ofreference index information of an encoded prediction block adjacent to aleft edge of the prediction block subject to encoding and outputs thereference index information, and in case that the partition mode is amode where the coding block is divided by a vertical border intoprediction blocks arranged horizontally, the reference index derivationunit (131) sets reference index information of a time merge candidate toa value of reference index information of an encoded prediction blockadjacent to an upper edge of the prediction block subject to encodingand outputs the reference index information.

According to yet another embodiment of the present invention, a movingpicture encoding method is provided. The method partitions a firstblock, which is obtained by partitioning each picture, into one or moresecond blocks and encodes a moving picture using inter prediction. Themethod includes: deriving a first inter prediction information candidatefrom inter prediction information of a third block in a proximity of thesecond block subject to encoding in a picture subject to encoding;deriving a second inter prediction information candidate from interprediction information of a fourth block at a position identical to orin a proximity of the second block subject to encoding in a picturedifferent from the picture subject to encoding; constructing aprediction information candidate list including a prediction informationcandidate to which, in case that the first inter prediction informationcandidate is derived, the derived first inter prediction informationcandidate is added, and in case that the second inter predictioninformation candidate is derived, the derived second inter predictioninformation candidate is added, respectively; selecting a candidate ofinter prediction information to be used for the inter prediction of thesecond block subject to encoding from the one or more predictioninformation candidates in the prediction information candidate list, anddetermining an index indicating inter prediction information; encodingthe index indicating inter prediction information to be used for theinter prediction of the second block subject to encoding. The derivingof the first inter prediction information candidate does not use, as thefirst inter prediction information candidate, coding information of afifth block included in a block identical to the first block includingthe second block subject to encoding.

According to an aspect of the present invention, a moving picturedecoding device is provided. The device decodes a bitstream where firstblock, which is obtained by partitioning each picture, is partitionedinto one or more second blocks and a moving picture is encoded by interprediction. The device includes: a first prediction informationderivation unit (230) configured to derive a first inter predictioninformation candidate from inter prediction information of a third blockin a proximity of the second block subject to decoding in a picturesubject to decoding; a second prediction information derivation unit(232) configured to derive a second inter prediction informationcandidate from inter prediction information of a fourth block at aposition identical to or in a proximity of the second block subject todecoding in a picture different from the picture subject to decoding; adecoding unit (202) configured to decode an index indicating interprediction information to be used for the inter prediction of the secondblock subject to decoding; a candidate list construction unit (233)configured to construct a prediction information candidate listincluding a prediction information candidate to which, in case that thefirst inter prediction information candidate is derived, the derivedfirst inter prediction information candidate is added, and in case thatthe second inter prediction information candidate is derived, thederived second inter prediction information candidate is added,respectively; and a selection unit (236) configured to select acandidate of inter prediction information to be used for the interprediction of the second block subject to decoding indicated by theindex from the one or more prediction information candidates in theprediction information candidate list. The first prediction informationderivation unit (230) does not use, as the first inter predictioninformation candidate, coding information of a fifth block included in ablock identical to the first block including the second block subject todecoding.

According to another aspect of the present invention, also a movingpicture decoding device is provided. The device partitions a decodingblock into one or more prediction blocks in accordance with a partitionmode so as to perform motion compensation prediction. The deviceincludes: a reference index derivation unit (231) configure to derive,in a merge mode where inter prediction information defined as a timemerge candidate is derived from inter prediction information of aprediction block at a position identical to or in a proximity of aprediction block subject to decoding in a decoded picture different intime from the prediction block subject to decoding and inter predictionof the prediction block subject to decoding is executed from the derivedinter prediction information, reference index information of a timemerge candidate as reference index information that specifies areference picture used in the prediction block subject to decoding; anda time merge candidate generating unit configured to derive interprediction information of time merge candidate based on the derivedreference index information. In case that the partition mode is a modewhere the decoding block is divided by a horizontal border intoprediction blocks arranged vertically, the reference index derivationunit (231) sets reference index information of a time merge candidate toa value of reference index information of an decoded prediction blockadjacent to a left edge of the prediction block subject to decoding andoutputs the reference index information, and in case that the partitionmode is a mode where the decoding block is divided by a vertical borderinto prediction blocks arranged horizontally, the reference indexderivation unit (231) sets reference index information of a time mergecandidate to a value of reference index information of an decodedprediction block adjacent to an upper edge of the prediction blocksubject to decoding and outputs the reference index information.

According to yet another aspect of the invention, a moving picturedecoding method is provided. The method decodes a bitstream where firstblock, which is obtained by partitioning each picture, is partitionedinto one or more second blocks and a moving picture is encoded by interprediction. The method includes: deriving a first inter predictioninformation candidate from inter prediction information of a third blockin a proximity of the second block subject to decoding in a picturesubject to decoding; deriving a second inter prediction informationcandidate from inter prediction information of a fourth block at aposition identical to or in a proximity of the second block subject todecoding in a picture different from the picture subject to decoding;decoding an index indicating inter prediction information to be used forthe inter prediction of the second block subject to decoding;constructing a prediction information candidate list including aprediction information candidate to which, in case that the first interprediction information candidate is derived, the derived first interprediction information candidate is added, and in case that the secondinter prediction information candidate is derived, the derived secondinter prediction information candidate is added, respectively; andselecting a candidate of inter prediction information to be used for theinter prediction of the second block subject to decoding indicated bythe index from the one or more prediction information candidates in theprediction information candidate list. The deriving of the first interprediction information candidate does not use, as the first interprediction information candidate, coding information of a fifth blockincluded in a block identical to the first block including the secondblock subject to decoding.

Optional combinations of the aforementioned constituting elements, andimplementations of the invention in the form of methods, apparatuses,systems, recording mediums, computer programs, or the like may also bepracticed as additional modes of the present invention.

According to the present invention, an amount of generated code ofcoding information to be transmitted can be reduced and an encodingefficiency can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a structure of a moving pictureencoding device that executes a method for predicting a motion vectoraccording to an embodiment;

FIG. 2 is a block diagram illustrating a structure of the moving picturedecoding device that executes a method for predicting a motion vectoraccording to the embodiment;

FIG. 3 illustrates a tree block and a coding block;

FIG. 4 illustrates a partition mode of a prediction block;

FIG. 5 illustrates a prediction block in the proximity of a predictionblock subject to processing of a spatial merge candidate in a mergemode;

FIG. 6 illustrates a prediction block in the proximity of a predictionblock subject to processing of a spatial merge candidate in a mergemode;

FIG. 7 illustrates a prediction block in the proximity of a predictionblock subject to processing of a spatial merge candidate in a mergemode;

FIG. 8 illustrates a prediction block in the proximity of a predictionblock subject to processing of a spatial merge candidate in a mergemode;

FIG. 9 illustrates a prediction block to be referred to when deriving atime merge candidate in a merge mode;

FIG. 10 illustrates syntax of a bitstream at a slice level regarding amerge mode;

FIG. 11 illustrates syntax of a bitstream at a prediction block levelregarding a merge mode;

FIG. 12 illustrates an example of an entropy code of a syntax element ofa merge index;

FIG. 13 is a block diagram showing a detailed configuration of an interprediction information derivation unit of the moving picture encodingdevice of FIG. 1;

FIG. 14 is a block diagram showing a detailed configuration of an interprediction information derivation unit of the moving picture decodingdevice of FIG. 2;

FIG. 15 illustrates a prediction block in the proximity of a predictionblock subject to processing in a merge mode;

FIG. 16 shows a flowchart illustrating a processing procedure ofsequential processing of merge candidate derivation process and mergecandidate list construction process;

FIG. 17 shows a flowchart illustrating a processing procedure ofparallel processing of merge candidate derivation process and mergecandidate list construction process;

FIG. 18 shows a flowchart illustrating procedure of derivation processof a merge candidate in a merge mode and construction process of a mergecandidate list;

FIG. 19 shows a flowchart illustrating procedure of derivation processof spatial merge candidate of a merge mode;

FIG. 20 illustrates an adjacent block referred to in derivation processof a reference index of a time merge candidate according to a firstexemplary embodiment of the present embodiment;

FIG. 21 shows a flowchart illustrating procedure of derivation processof a reference index of a time merge candidate of a merge mode accordingto a method of the first exemplary embodiment;

FIG. 22 illustrates an adjacent block referred to in derivation processof a reference index of a time merge candidate according to a secondexemplary embodiment of the present embodiment;

FIG. 23 shows a flowchart illustrating procedure of derivation processof a reference index of a time merge candidate of a merge mode accordingto a method of the second exemplary embodiment;

FIG. 24 illustrates an adjacent block referred to in derivation processof a reference index of a time merge candidate according to a thirdexemplary embodiment of the present embodiment;

FIG. 25 shows a flowchart illustrating procedure of derivation processof a reference index of a time merge candidate of a merge mode accordingto a method of the third exemplary embodiment;

FIG. 26 illustrates an adjacent block referred to in derivation processof a reference index of a time merge candidate according to a fourthexemplary embodiment of the present embodiment;

FIG. 27 shows a flowchart illustrating procedure of derivation processof a reference index of a time merge candidate of a merge mode accordingto a method of the fourth exemplary embodiment;

FIG. 28 illustrates an adjacent block referred to in derivation processof a reference index of a time merge candidate according to a fifthexemplary embodiment of the present embodiment;

FIG. 29 shows a flowchart illustrating procedure of derivation processof a reference index of a time merge candidate of a merge mode accordingto a method of the fifth exemplary embodiment;

FIG. 30 shows a flowchart illustrating procedure of derivation processof a reference index of a time merge candidate of a merge mode accordingto a method of a sixth exemplary embodiment;

FIG. 31 illustrates an adjacent block referred to in derivation processof a reference index of a time merge candidate according to a seventhexemplary embodiment of the present embodiment;

FIG. 32 shows a flowchart illustrating procedure of derivation processof a reference index of a time merge candidate of a merge mode accordingto the method of the seventh exemplary embodiment;

FIG. 33 illustrates an adjacent block referred to in derivation processof a reference index of a coding block of N by N partition.

FIG. 34 shows a flowchart illustrating procedure of derivation processof a time merge candidate in a merge mode;

FIG. 35 shows a flowchart illustrating procedure of derivation processof a picture of a different time in a merge mode;

FIG. 36 shows a flowchart illustrating procedure of derivation processof a prediction block of a picture of a different time in a merge mode;

FIG. 37 shows a flowchart illustrating procedure of derivation processof a time merge candidate in a merge mode;

FIG. 38 shows a flowchart illustrating procedure of derivation processof a time merge candidate in a merge mode;

FIG. 39 shows a flowchart illustrating procedure of scaling computationprocess of a motion vector;

FIG. 40 shows a flowchart illustrating procedure of scaling computationprocess of a motion vector;

FIG. 41 shows a flowchart illustrating procedure of construction processof a merge candidate list in a merge mode;

FIG. 42 illustrates a time direct mode according to conventional MPEG-4AVC/H.264;

FIG. 43 illustrates an adjacent block referred to in derivation processof a reference index of a time merge candidate according to an eighthexemplary embodiment of the present embodiment; and

FIG. 44 shows a flowchart illustrating procedure of derivation processof a reference index of a time merge candidate in a merge mode accordingto a method of the eighth exemplary embodiment.

DETAILED DESCRIPTION OF THE INVENTION

According to the present embodiment, in relation with encoding of amoving picture, more specifically in order to increase encodingefficiency in moving picture encoding where a picture is partitionedinto rectangular blocks of an arbitrary size and shape and motioncompensation is performed between pictures in units of blocks, aplurality of motion vector predictors are derived from a motion vectorof a block in the proximity of a block subject to encoding or from amotion vector of a block of an encoded picture, a difference vectorbetween a motion vector of the block subject to encoding and a selectedmotion vector predictor is calculated, and the difference vector isencoded so as to reduce the amount of code. Alternatively, by usingcoding information of a block in the proximity of a block subject toencoding or a block of an encoded picture, coding information of theblock subject to encoding is derived so as to reduce the amount of code.In case of decoding a moving picture, a plurality of motion vectorpredictors are calculated from a motion vector of a block in theproximity of a block subject to decoding or from a motion vector of ablock of a decoded picture, a motion vector of the block subject todecoding is calculated from a difference vector decoded from a bitstreamand from a selected motion vector predictor so as to decode the blocksubject to decoding. Alternatively, by using coding information of ablock in the proximity of a block subject to decoding, or a block of adecoded picture, coding information of a block subject to decoding isderived.

First, definitions will be given for technologies and technical termsused in the present embodiment.

(Regarding a Tree Block and a Coding Block)

According to the embodiment, a picture is partitioned in units ofsquares having a same arbitrary size as shown in FIG. 3. This unit isdefined as a tree block and used as a basic unit of managing an addressfor specifying a block subject to encoding or decoding (Hereinafter, “ablock subject to encoding or decoding” refers to a block subject toencoding in case of encoding process, and refers to a block subject todecoding in case of decoding process, unless otherwise noted.) in apicture. A tree block comprises one brightness signal and twocolor-difference signals, except in case of a monochrome. The size of atree block can be determined freely in units of powers of 2 inaccordance with the size of a picture and/or a texture in the picture.In order to optimize encoding process in accordance with a texture in apicture, a tree block can be hierarchically partitioned into four blocks(divided by two both vertically and horizontally) having a smaller blocksize, as necessary, by dividing a brightness signal and color-differencesignals in the tree block. These blocks are defined as coding blocksrespectively, and used as basic units in encoding and decoding. A codingblock also comprises one brightness signal and two color-differencesignals, except in case of a monochrome. The maximum size of a codingblock is as same as the size of a tree block. A coding block of minimumsize is referred to as a minimum coding block, and the size thereof canbe set freely in units of powers of 2.

In FIG. 3, a coding block A is defined by using a tree block as onecoding block without partitioning the tree block. A coding block B is acoding block made by partitioning a tree block into four blocks. Acoding block C is a coding block made by further partitioning a block,which is obtained by partitioning a tree block into four, into fourblocks. A coding block D is a coding block made by further partitioninga block, which is obtained by partitioning a tree block into four, intofour blocks twice hierarchically. The coding block D is a coding blockof the minimum size.

(Regarding a Prediction Mode)

A mode is switched between intra prediction (MODE_INTRA) and interprediction (MODE_INTER) in units of coding blocks. With the intraprediction, prediction is performed from a surrounding encoded ordecoded picture signals in a picture subject to encoding or decoding (Incase of encoding process, “decoded” is used for a decoded picture thathas been encoded in a encoding process, a decode prediction block thathas been encoded in a encoding process, a decoded picture signal thathas been encoded in a encoding process, or the like, and in case ofdecoding process, “decoded” is used for a decoded picture, a decodedprediction block, a decoded picture signal, or the like. The same shallapply herein after unless otherwise noted.). This mode thatdistinguishes the intra prediction (MODE_INTRA) and the inter prediction(MODE_INTER) is defined as a prediction mode (PredMode). The predictionmode (PredMode) has, as a value, the intra prediction (MODE_INTRA) orthe inter prediction (MODE_INTER), and can select a type of predictionso as to perform encoding.

(Regarding a Partition Mode, a Prediction Block, and a Prediction Unit)

In case of partitioning a picture into blocks and performing intraprediction (MODE_INTRA) and inter prediction (MODE_INTER), a codingblock is partitioned as necessary so as to perform prediction in orderto set a smaller unit for switching methods of intra prediction andinter prediction. This mode that distinguishes a method for partitioninga brightness signal and color-difference signals of a coding block isdefined as a partition mode (PartMode). In addition, the partitionedblock thereof is defined as a prediction block. As shown in FIG. 4,eight types of partition modes (PartMode) are defined in accordance witha method for partitioning a brightness signal of a coding block.

A partition mode (PartMode) where a brightness signal of a coding blockis not partitioned and regarded as one prediction block as shown in FIG.4A is defined as 2N by 2N partition (PART_2N×2N). Partition modes(PartMode) where a brightness signal of a coding block is partitionedinto two prediction blocks arranged vertically as shown in FIGS. 4B, 4C,and 4D are defined as 2N by N partition (PART_2N×N), 2N by nU partition(PART_2N×nU), and 2N by nD partition (PART_2N×nD), respectively. The 2Nby N partition (PART_2N×N) is a partition mode where a block ispartitioned with a ratio of 1:1, vertically, the 2N by nU partition(PART_2N×nU) is a partition mode where a block is partitioned with aratio of 1:3, vertically, and 2N by nD partition (PART_2N×nD) is apartition mode where a block is partitioned with a ratio of 3:1,vertically. Partition modes (PartMode) where a brightness signal of acoding block is partitioned into two prediction blocks arrangedhorizontally as shown in FIGS. 4E, 4F, and 4G are defined as N by 2Npartition (PART_N×2N), nL by 2N partition (PART_nL×2N), and nR by 2Npartition (PART_nR×2N), respectively. The N by 2N partition (PART_N×2N)is a partition mode where a block is partitioned with a ratio of 1:1,horizontally, the nL by 2N partition (PART_nL×2N) is a partition modewhere a block is partitioned with a ratio of 1:3, horizontally, and nRby 2N partition (PART_nR×2N) is a partition mode where a block ispartitioned with a ratio of 3:1, horizontally. A partition mode(PartMode) where a brightness signal of a coding block is partitionedvertically and horizontally into four blocks as shown in FIG. 4H isdefined as N by N partition (PART_N×N).

For each partition mode (PartMode), a color-difference signal is alsopartitioned in a similar manner to that of horizontal and verticalpartition ratio of a brightness signal.

In a coding block, in order to identify each prediction block, a numberstarting from 0 is assigned to a prediction block in the coding block inthe order of encoding. This number is defined as a partition indexPartIdx. A number written in each prediction block in the coding blocksshown in FIG. 4 indicates the partition index PartIdx of the predictionblock. For the 2N by N partition (PART_2N×N), the 2N by nU partition(PART_2N×nU), and the 2N by nD partition (PART_2N×nD) shown in FIGS. 4B,4C, and 4D respectively, the partition index PartIdx of an upperprediction block is set to 0 and the partition index PartIdx of a lowerprediction block is set to 1. For the N by 2N partition (PART_N×2N), thenL by 2N partition (PART_nL×2N), and the nR by 2N partition (PART_nR×2N)shown in FIGS. 4E, 4F, and 4G respectively, the partition index PartIdxof a left prediction block is set to 0 and the partition index PartIdxof a right prediction block is set to 1. For the N by N partition(PART_N×N) shown in FIG. 4H, the partition index PartIdx of an upperleft prediction block is set to 0, the partition index PartIdx of anupper right prediction block is set to 1, the partition index PartIdx ofa lower left prediction block is set to 2, and the partition indexPartIdx of a lower right prediction block is set to 3.

In case that the prediction mode (PredMode) is inter prediction(MODE_INTER), the 2N by 2N partition (PART_2N×2N), the 2N by N partition(PART_2N×N), the 2N by nU partition (PART_2N×nU), the 2N by nD partition(PART_2N×nD), the N by 2N partition (PART_N×2N), the nL by 2N partition(PART_nL×2N), and the nR by 2N partition (PART_nR×2N) are defined as apartition mode (PartMode). Only in case of the coding block D, which isthe minimum coding block, the N by N partition (PART_N×N) can be definedas a partition mode (PartMode) in addition to the 2N by 2N partition(PART_2N×2N), the 2N by N partition (PART_2N×N), the 2N by nU partition(PART_2N×nU), the 2N by nD partition (PART_2N×nD), the N by 2N partition(PART_N×2N), the nL by 2N partition (PART_nL×2N), and the nR by 2Npartition (PART_nR×2N). However, it is assumed that the N by N partition(PART_N×N) is not defined as a partition mode (PartMode) according tothe present embodiment.

In case that the prediction mode (PredMode) is intra prediction(MODE_INTRA), only the 2N by 2N partition (PART_2N×2N) is defined as apartition mode (PartMode) for blocks except for the coding block D,which is the minimum coding block. Only in case of the coding block D,which is the minimum coding block, the N by N partition (PART_N×N) isdefined as a partition mode (PartMode) in addition to the 2N by 2Npartition (PART_2N×2N). The reason why the N by N partition (PART_N×N)is not defined except for the minimum coding block, is that coding blockother than the minimum coding block can be partitioned into four blocksso as to represent smaller coding blocks.

(Regarding the Position of a Tree Block, a Coding Block, a PredictionBlock, and a Transformation Block)

The position of each block such as a tree block, a coding block, aprediction block, a transformation block, or the like according to thepresent embodiment is represented by two dimensional coordinates wherethe position of the top left pixel of brightness signal in a screen ofbrightness signals is defined as the original point, and the position ofthe top left pixel of brightness signal included in the area of eachblock is represented by two dimensional coordinates (X, Y). Regardingthe directions of coordinate axes, the positive directions are thehorizontally-right direction and the vertically-down direction,respectively. The unit of scale is pixel of brightness signal. Theposition of each block of color-difference signals is represented bycoordinates of a pixel of a brightness signal included in an area of theblock and the unit of scale is pixel, not only in case that acolor-difference format is 4:4:4 where the picture sizes (the numbers ofpixels) for brightness signals and color-difference signals areidentical to each other, but also in case that the color-differenceformat is 4:2:0 or 4:2:2 where the picture sizes (the numbers of pixels)of brightness signals and color-difference signals are different. Inthis manner, not only the position of each block of color-differencesignals can be identified, but also mere comparison of coordinate valuesclarifies a positional relationship between a block of brightnesssignals and a block of color-difference signals.

(Regarding an Inter Prediction Mode and a Reference List)

According to the embodiment of the invention, a plurality of decodedpictures can be used as a reference picture in inter prediction where aprediction is made on the basis of picture signals of a decoded picture.In order to identify a reference picture selected from a plurality ofreference pictures, a reference index is assigned for each predictionblock. For a B slice, two arbitrary reference pictures can be selectedfor each prediction block so as to perform inter prediction. The interprediction modes includes L0 prediction (Pred_L0), L1 prediction(Pred_L1), and bi-prediction (Pred_BI). The reference picture is managedby L0 (reference list 0) and L1 (reference list 1), which are liststructures, and a reference picture can be identified by specifying areference index of L0 or L1. The L0 prediction (Pred_L0) is interprediction that refers to a reference picture managed by L0, the L1prediction (Pred_L1) is inter prediction that refers to a referencepicture managed by L1, and the bi-prediction (Pred_BI) is predictionwhere both L0 prediction and L1 prediction are performed, and onereference picture managed by L0 and one reference picture managed by L1are referred to. In inter prediction of a P slice, only L0 predictioncan be used. In inter prediction of a B slice, L0 prediction, L1prediction, and bi-prediction where L0 prediction and L1 prediction areaveraged or added with weights, can be used. For invariables andvariables to which a suffix LX is attached to output in the followingprocesses, it is assumed that the process is performed for each of L0and L1.

(a Merge Mode and a Merge Candidate)

A merge mode is not a mode that encode or decode inter predictioninformation (e.g., a prediction mode, a reference index, a motionvector, or the like) of a prediction block subject to encoding ordecoding, but is a mode that performs inter prediction by deriving interprediction information of a prediction block subject to encoding ordecoding from inter prediction information of: a prediction block thatis in a same picture with the prediction block subject to encoding ordecoding and that is in the proximity of the prediction block subject toencoding or decoding; or a prediction block that is in a picturedifferent in time from a picture of the prediction block subject toencoding or decoding, and that is at a position identical to or in theproximity (at a position in the proximity of) of the prediction blocksubject to encoding or decoding. A prediction block and the interprediction information thereof, the prediction block being in a samepicture with the prediction block subject to encoding or decoding andbeing in the proximity of the prediction block subject to encoding ordecoding, is used as a spatial merge candidate. Inter predictioninformation derived from a prediction block and inter predictioninformation thereof, the prediction block being in an encoded or decodedpicture different in time from a picture of the prediction block subjectto encoding or decoding and being at a position identical to or in theproximity (at a position in the proximity) of the prediction blocksubject to encoding or decoding, is used as a time merge candidate. Eachmerge candidate is registered in a merge candidate list, and a mergecandidate to be used for inter prediction is specified by a merge index.

(Regarding a Prediction Block in the Proximity)

FIGS. 5, 6, 7, and 8 illustrate: a deprivation of a spatial mergecandidate; and a prediction block to be referred to when deriving aspatial merge candidate and when deriving the reference index of a timemerge candidate, the prediction block being in a same picture with theprediction block subject to encoding or decoding and being in theproximity of the prediction block subject to encoding or decoding. FIG.9 illustrates a prediction block to be referred to when deriving thereference index of a time merge candidate, the prediction block being inan encoded or decoded picture different in time from the predictionblock subject to encoding or decoding and being at a position identicalto or in the proximity of the prediction block subject to encoding ordecoding. By referring to FIGS. 5, 6, 7, 8, and 9, an explanation willbe given on a prediction block in the spatial proximity of theprediction block subject to encoding or decoding, and on a predictionblock at an identical position but different in time.

As shown in FIG. 5, in a same picture with the prediction block subjectto encoding or decoding, a prediction block A adjacent to the left edgeof the prediction block subject to encoding or decoding, a predictionblock B adjacent to the upper edge thereof, a prediction block Cadjacent to the upper right vertex thereof, a prediction block Dadjacent to the lower left vertex thereof, and a prediction block Eadjacent to the upper left vertex thereof are defined as a predictionblock in the spatial proximity.

As shown in FIG. 6, if there are a plurality of prediction blocks, ofwhich the sizes are smaller than the prediction block subject toencoding or decoding and which are adjacent to the left edge of theprediction block subject to encoding or decoding, a prediction block A10at the lowest position among the plurality of prediction blocks adjacentto the left edge is defined as a prediction block A adjacent to the leftedge according to the present embodiment.

In a similar manner, If there are a plurality of prediction blocks, ofwhich the sizes are smaller than the prediction block subject toencoding or decoding and which are adjacent to the upper edge of theprediction block subject to encoding or decoding, a prediction block B10at the right most position among the plurality of prediction blocksadjacent to the upper edge is defined as a prediction block B1 adjacentto the upper edge according to the present embodiment.

As shown in FIG. 7, also in case that the size of a prediction block Fadjacent to the left edge of the prediction block subject to encoding ordecoding is bigger than the prediction block subject to encoding ordecoding, in accordance with the conditions described above, theprediction block A is defined as a prediction block A if the predictionblock A is adjacent to the left edge of the prediction block subject toencoding or decoding, is defined as a prediction block D in case ofbeing adjacent to the lower left vertex of the prediction block subjectto encoding or decoding, and is defined as a prediction block E in caseof being adjacent to the upper left vertex of the prediction blocksubject to encoding or decoding. According to the example shown in FIG.6, a prediction block A, a prediction block E, and a prediction block Eare an identical prediction block.

As shown in FIG. 8, also in case that the size of a prediction block Gadjacent to the upper edge of the prediction block subject to encodingor decoding is bigger than the prediction block subject to encoding ordecoding, in accordance with the conditions described above, theprediction block G is defined as a prediction block B if the predictionblock G is adjacent to the upper edge of the prediction block subject toencoding or decoding, is defined as a prediction block C if theprediction block G is adjacent to the upper right vertex of theprediction block subject to encoding or decoding, and is defined as aprediction block E if the prediction block G is adjacent to the upperleft vertex of the prediction block subject to encoding or decoding.According to the example shown in FIG. 8, a prediction block B, aprediction block C, and a prediction block E are an identical predictionblock.

As shown in FIG. 9, an encoded or decoded prediction blocks T0 and T1 ina picture different in time from a picture of the prediction blocksubject to encoding or decoding and at a position identical to or in theproximity of the prediction block subject to encoding or decoding aredefined as a prediction block at a same position different in time.

(Regarding POC)

POC is defined as a parameter that is associated with a picture subjectto encoding, and a value that increases one at a time in the outputorder of pictures is defined as PCD. By the value of POC, whether or notpictures are identical with each other can be determined, whether apicture is previous to or subsequent to another picture in an outputorder can be determined, or a distance between pictures can be derived.For example, in case that POCs of two pictures have an identical value,the pictures can be determined to be an identical picture. In case thatPOCs of two pictures have different values, a picture with a smaller POCvalue is determined to be a picture that is to be output before theother picture, and a difference between POCs of two pictures representsa distance between the pictures along the time axis.

An explanation will be given below on the embodiment of the inventionwhile referring to figures. FIG. 1 is a block diagram showing astructure of a moving picture encoding device according to an embodimentof the invention. The moving picture encoding device according to theembodiment comprises a picture memory 101, a motion vector detectionunit 102, a motion vector difference calculation unit 103, an interprediction information derivation unit 104, a motion compensationprediction unit 105, an intra prediction unit 106, a prediction methoddetermining unit 107, a residual signal generating unit 108, anorthogonal transformation/quantization unit 109, a first bitstreamgenerating unit 110, a second bitstream generating unit 111, amultiplexing unit 112, an inverse quantization/inverse orthogonaltransformation unit 113, a decoded picture signal convolution unit 114,a coding information storing memory 115, and a decoded picture memory116.

The picture memory 101 temporarily stores a picture signal of a picturesubject to encoding, the signal having been provided in the order ofcapturing and/or in the order of display time. The picture memory 101provides the stored picture signal of a picture subject to encoding, inunits of predetermined pixel blocks, to the motion vector detection unit102, the prediction method determining unit 107, and the residual signalgenerating unit 108. In this process, the picture signals of picturesstored in the order of capturing and/or in the order of display time arerearranged in the order of encoding, and outputted from the picturememory 101 in units of pixel blocks.

The motion vector detection unit 102 detects motion vectors forrespective prediction block size and respective prediction modes foreach prediction block by block matching or the like between a picturesignal provided from the picture memory 101 and a reference pictureprovided from the decoded picture memory 116. The motion vectordetection unit 102 provides the detected motion vector to the motioncompensation prediction unit 105, the motion vector differencecalculation unit 103, and the prediction method determining unit 107.

By using coding information of a picture signal already encoded andstored in the coding information storing memory 115, the motion vectordifference calculation unit 103 calculates a plurality of candidates ofa motion vector predictor and stores the candidates in a motion vectorpredictor list, selects an optimal motion vector predictor from theplurality of candidates of a motion vector predictor registered in themotion vector predictor list, calculates a motion vector difference fromthe motion vector detected by the motion vector detection unit 102 andfrom the motion vector predictor, and provides the calculated motionvector difference to the prediction method determining unit 107.Further, the motion vector difference calculation unit 103 provides theprediction method determining unit 107 with a motion vector predictorindex that specifies a motion vector predictor selected from thecandidates of a motion vector predictor registered in the motion vectorpredictor list.

The inter prediction information derivation unit 104 derives a mergecandidate in a merge mode. By using coding information of a predictionblock having already been encoded and stored in the coding informationstoring memory 115, the inter prediction information derivation unit 104derives a plurality of merge candidates and registers the candidates ina merge candidate list, which will be described below, selects anappropriate merge candidate from the plurality of merge candidatesregistered in the merge candidate list, provides the motion compensationprediction unit 105 with inter prediction information (e.g., flagspredFlagL0[xP][yP] and predFlagL1[xP][yP] indicating whether or not touse L0 prediction and/or L1 prediction, reference indexesrefIdxL0[xP][yP] and refIdxL1[xP][yP], motion vectors mvL0[xP][yP] andmvL1[xP][yP], or the like) of each prediction block of the selectedmerge candidate, and provides the prediction method determining unit 107with a merge index that specifies the selected merge candidate. xP andyP are indexes indicating the position of an upper left pixel in aprediction block in a picture. The detailed configuration and operationof the inter prediction information derivation unit 104 will be givenlater.

The motion compensation prediction unit 105 generates from a referencepicture a prediction picture signal by inter prediction (motioncompensation prediction) by using a motion vector detected by the motionvector detection unit 102 and the inter prediction informationderivation unit 104, and provides the prediction picture signal to theprediction method determining unit 107. In L0 prediction and in L1prediction, one-directional prediction is performed. In case ofbi-prediction (Pred_BI), prediction for two directions are performed,respective inter-predicted signals for L0 prediction and L1 predictionare multiplied by a weighting coefficient adaptively, an offset value isadded, and convolution is performed so as to generate an ultimateprediction picture signal.

The intra prediction unit 106 performs intra prediction for each intraprediction mode. The intra prediction unit 106 generates a predictionpicture signal by intra prediction from a decoded picture signal storedin the decoded picture memory 211, selects an appropriate intraprediction mode from a plurality of intra prediction modes, and providesthe prediction method determining unit 107 with a selected intraprediction mode and a prediction picture signal according to theselected intra prediction mode.

The prediction method determining unit 107 determines a prediction modePredMode and a partition mode PartMode that determine inter prediction(PRED_INTER) or intra prediction (PRED_INTRA) in units of optimal codingblocks from a plurality of prediction methods, by evaluating an amountof code of coding information and a residual signal, an amount ofdistortion between a prediction picture signal and a picture signal orthe like for respective prediction methods. In case of inter prediction(PRED_INTER), the prediction method determining unit 107 determineswhether or not a mode is a merge mode in units of prediction blocks. Incase that the mode is a merge mode, the prediction method determiningunit 107 determines a merge index, and in case that the mode is not amerge mode, determines an inter prediction mode, a motion vectorpredictor index, reference indexes of L0 and L1, a motion vectordifference, or the like, and provides the first bitstream generatingunit 110 with coding information according to the determination.

Further, the prediction method determining unit 107 stores informationindicating the determined prediction method, and coding informationincluding a motion vector or the like according to the determinedprediction method in the coding information storing memory 115. Thecoding information to be stored includes: a prediction mode PredMode anda partition mode PartMode of respective coding blocks; flagspredFlagL0[xP][yP] and predFlagL1[xP][yP] indicating whether or not touse L0 prediction and L1 prediction of each prediction block; referenceindexes refIdxL0[xP][yP] and refIdxL1[xP][yP] of L0 and L1; motionvectors mvL0[xP][yP] and mvL1[xP][yP] of L0 and L1; or the like. xP andyP are indexes indicating the position of an upper left pixel in aprediction block in a picture. In case that the prediction mode PredModeis intra prediction (MODE_INTRA), both flags, predFlagL0[xP][yP]indicating whether or not to use L0 prediction and predFlagL1[xP][yP]indicating whether or not to use L1 prediction, are 0. On the otherhand, in case that the prediction mode PredMode is inter prediction(MODE_INTER) and the inter prediction mode is L0 prediction (Pred_L0),the flag predFlagL0[xP][yP] indicating whether or not to use L0prediction is 1, and the flag predFlagL1[xP][yP] indicating whether ornot to use L1 prediction is 0. In case that the inter prediction mode isL1 prediction (Pred_L1), the flag predFlagL0[xP][yP] indicating whetheror not to use L0 prediction is 0, and the flag predFlagL1[xP][yP]indicating whether or not to use L1 prediction is 1. In case that theinter prediction mode is bi-prediction (Pred_BI), both flags,predFlagL0[xP][yP] indicating whether or not to use L0 prediction andpredFlagL1[xP][yP] indicating whether or not to use L1 prediction,are 1. The prediction method determining unit 107 provides the residualsignal generating unit 108 and the decoded picture signal convolutionunit 114 with a prediction picture signal according to the determinedprediction mode.

The residual signal generating unit 108 generates a residual signal byperforming subtraction between a picture signal subject to encoding anda prediction picture signal, and provides the residual signal to theorthogonal transformation/quantization unit 109. The orthogonaltransformation/quantization unit 109 performs orthogonal transformationand quantization on the residual signal in accordance with aquantization parameter so as to generate orthogonally-transformed andquantized residual signal and provides the orthogonally-transformed andquantized residual signal to the second bitstream generating unit 111and to the inverse quantization/inverse orthogonal transformation unit113. Further, the orthogonal transformation/quantization unit 109 storesthe quantization parameter in the coding information storing memory 115.

the first bitstream generating unit 110 encodes coding informationaccording to a prediction method determined for each coding block andeach prediction block by the prediction method determining unit 107, inaddition to information for each sequence, each picture, each slice, andeach coding block. More specifically, the first bitstream generatingunit 110 encodes coding information, such as, a prediction mode PredModefor each coding block, a partition mode PartMode, a flag determiningwhether or not a mode is a merge mode in case of inter prediction(PRED_INTER), a merge index in case of merge mode, an inter predictionmode in case that the mode is not a merge mode, a motion vectorpredictor index, information regarding a motion vector difference, orthe like, in accordance with a prescribed syntax rule, which will bedescribed later, so as to generate a first bitstream and provides thefirst bitstream to the multiplexing unit 112.

The second bitstream generating unit 111 entropy encodes theorthogonally-transformed and quantized residual signal in accordancewith a prescribed syntax rule so as to generate a second bitstream andprovides the second bitstream to the multiplexing unit 112. In themultiplexing unit 112, the first bitstream and the second bitstream aremultiplexed in accordance with a prescribed syntax rule so as togenerate a bitstream.

The inverse quantization/inverse orthogonal transformation unit 113inverse quantizes and inverse-orthogonally transforms theorthogonally-transformed and quantized residual signal provided from theorthogonal transformation/quantization unit 109 so as to calculate aresidual signal, and provide the residual signal to the decoded picturesignal convolution unit 114. The decoded picture signal convolution unit114 convolves the prediction picture signal according to thedetermination by the prediction method determining unit 107 and theresidual signal that is inverse-quantized andinverse-orthogonally-transformed in the inverse quantization/inverseorthogonal transformation unit 113 so as to generate a decoded pictureand stores the decoded picture in the decoded picture memory 116.Depending on circumstances, a filtering process that reduces distortionsuch as block distortion or the like caused by coding is performed onthe decoded picture and the decoded picture is stored in the decodedpicture memory 116, accordingly.

FIG. 1 is a block diagram showing a structure of a moving picturedecoding device according to an embodiment of the invention, the movingpicture decoding device corresponding to the moving picture encodingdevice of FIG. 1. The moving picture decoding device according to theembodiment comprises a separation unit 201, a first bitstream decodingunit 202, a second bitstream decoding unit 203, a motion vectorcalculation unit 204, an inter prediction information derivation unit205, a motion compensation prediction unit 206, an intra prediction unit207, an inverse quantization/inverse orthogonal transformation unit 208,a decoded picture signal convolution unit 209, a coding informationstoring memory 210, and a decoded picture memory 211.

Decoding process of the moving picture decoding device of FIG. 2corresponds to the decoding process provided in the moving pictureencoding device of FIG. 1. Therefore, respective configurations of themotion compensation prediction unit 206, the inversequantization/inverse orthogonal transformation unit 208, the decodedpicture signal convolution unit 209, the coding information storingmemory 210, and the decoded picture memory 211 of FIG. 2 have a functioncorresponding to respective configurations of the motion compensationprediction unit 105, the inverse quantization/inverse orthogonaltransformation unit 113, the decoded picture signal convolution unit114, the coding information storing memory 115, and the decoded picturememory 116 of the moving picture encoding device of FIG. 1.

The bitstream provided to the separation unit 201 is separated inaccordance with a prescribed syntax rule. The separated first bitstreamis provided to the first bitstream decoding unit 202, and the secondbitstream is provided to the second bitstream decoding unit 203.

The first bitstream decoding unit 202 decodes the provided bitstream andobtains information for each sequence, each picture, each slice, andeach coding block, and coding information for each prediction block.More specifically, the first bitstream decoding unit 202 decodes codinginformation regarding, for example, a prediction mode PredMode thatdetermines whether prediction is inter prediction (PRED_INTER) or intraprediction (PRED_INTRA) for each coding block, a partition modePartMode, a flag determines whether or not a mode is a merge mode incase of inter prediction (PRED_INTER), a merge index in case that themode is a merge mode, an inter prediction mode in case that the mode isnot a merge mode, a motion vector predictor index, a motion vectordifference, or the like, in accordance with a prescribed syntax rule,which will be described later, and provides the coding information tothe motion vector calculation unit 204, the inter prediction informationderivation unit 205 or the intra prediction unit 207.

The second bitstream decoding unit 203 decodes the provided bitstream soas to calculate an orthogonally-transformed and quantized residualsignal and provides the orthogonally-transformed and quantized residualsignal to the inverse quantization/inverse orthogonal transformationunit 208.

If the prediction mode PredMode of a prediction block subject todecoding is inter prediction (PRED_INTER) and not a merge mode, themotion vector calculation unit 204 derives, by using coding informationof a picture signal already decoded and stored in the coding informationstoring memory 210, a plurality of candidates of a motion vectorpredictor and registers the candidates in a motion vector predictorlist, which will be described later. The motion vector calculation unit204 selects a motion vector predictor according to a motion vectorpredictor index, which is decoded in the first bitstream decoding unit202 and provided, from the plurality of candidates of a motion vectorpredictor registered in the motion vector predictor list, calculates amotion vector from the difference vector decoded in the first bitstreamdecoding unit 202 and from the selected motion vector predictor. Themotion vector calculation unit 204 provides the motion compensationprediction unit 206 with the motion vector with other codinginformation, and stores the motion vector and other coding informationin the coding information storing memory 210. The coding information tobe provided and stored in this process includes: a prediction modePredMode; partition mode PartMode; flags predFlagL0[xP][yP] andpredFlagL1[xP][yP] indicating whether or not to use L0 prediction and L1prediction respectively; reference indexes refIdxL0[xP][yP] andrefIdxL1[xP][yP] of L0 and L1; motion vectors mvL0[xP][yP] andmvL1[xP][yP] of L0 and L1; or the like. xP and yP are indexes indicatingthe position of an upper left pixel in a prediction block in a picture.In case that the prediction mode PredMode is inter prediction(MODE_INTER) and the inter prediction mode is L0 prediction (Pred_L0),the flag predFlagL0 indicating whether or not to use L0 prediction is 1,and the flag predFlagL1 indicating whether or not to use L1 predictionis 0. In case that the inter prediction mode is L1 prediction (Pred_L1),the flag predFlagL0 indicating whether or not to use L0 prediction is 0,and the flag predFlagL1 indicating whether or not to use L1 predictionis 1. In case that the inter prediction mode is bi-prediction (Pred_BI),a flag predFlagL0 indicating whether or not to use L0 prediction and aflag predFlagL1[xP][yP] indicating whether or not to use L1 predictionare both 1.

If the prediction mode PredMode of a prediction block subject todecoding is inter prediction (PRED_INTER) and if the mode is a mergemode, the inter prediction information derivation unit 205 derives amerge candidate. By using coding information of a prediction blockhaving already been decoded and stored in the coding information storingmemory 115, the inter prediction information derivation unit 205 derivesa plurality of merge candidates and registers the candidates in a mergecandidate list, which will be described later. The inter predictioninformation derivation unit 205 selects, from the plurality of mergecandidates registered in the merge candidate list, a merge candidatecorresponding to a merge index that is decoded in the first bitstreamdecoding unit 202 and provided. The inter prediction informationderivation unit 205 provides the motion compensation prediction unit 206with inter prediction information of the selected merge candidate suchas, flags predFlagL0[xP][yP] and predFlagL1[xP][yP] indicating whetheror not to use L0 prediction and L1 prediction, reference indexesrefIdxL0[xP][yP] and refIdxL1[xP][yP] of L0 and L1, motion vectorsmvL0[xP][yP] and mvL1[xP][yP] of L0 and L1, or the like, and stores theinter prediction information in the coding information storing memory210. xP and yP are indexes indicating the position of an upper leftpixel in a prediction block in a picture. The detail on theconfiguration and operation of the inter prediction informationderivation unit 205 will be given later.

The motion compensation prediction unit 206 generates a predictionpicture signal by inter prediction (motion compensation prediction) byusing inter prediction information calculated in the motion vectorcalculation unit 204 or in the inter prediction information derivationunit 205 from a reference picture stored in the decoded picture memory211, and provides the prediction picture signal to the decoded picturesignal convolution unit 209. In case of bi-prediction (Pred_BI), twomotion compensation prediction picture signals of L0 prediction and L1prediction are multiplied by a weighting coefficient adaptively, andconvolution is performed so as to generate an ultimate predictionpicture signal.

The intra prediction unit 207 performs intra prediction when theprediction mode PredMode of a prediction block to be decoded is intraprediction (PRED_INTRA). The coding information decoded in the firstbitstream decoding unit includes an intra prediction mode. Based on theintra prediction mode, a prediction picture signal is generated by intraprediction from the decoded picture signal stored in the decoded picturememory 211, and provided to the decoded picture signal convolution unit209. Both flags, predFlagL0[xP][yP] and predFlagL1[xP][yP] indicatingwhether or not to use L0 prediction and L1 prediction, are set to 0 andstored in the coding information storing memory 210. xP and yP areindexes indicating the position of an upper left pixel in a predictionblock in a picture.

The inverse quantization/inverse orthogonal transformation unit 208inverse-orthogonally transforms and inverse quantizes theorthogonally-transformed and quantized residual signal, which is decodedin the first bitstream decoding unit 202, and obtains aninverse-orthogonally transformed and inverse quantized residual signal.

The decoded picture signal convolution unit 209 decodes a decodedpicture signal by convolving the prediction picture signal that is interpredicted in the motion compensation prediction unit 206 or theprediction picture signal that is intra predicted in the intraprediction unit 207 and the residual signal that isinverse-orthogonally-transformed and inverse-quantized by the inversequantization/inverse orthogonal transformation unit 208, and stores thedecoded picture signal in the decoded picture memory 211. When thedecoded picture is stored in the decoded picture memory 211, a filteringprocess that reduces distortion such as block distortion or the likecaused by coding is performed on the decoded picture and the decodedpicture is stored in the decoded picture memory 211, depending oncircumstances.

(Regarding Syntax)

Next, an explanation will be given on syntax that is a common rule forencoding and decoding of a bitstream of a moving picture, which isencoded by a moving picture encoding device provided with a method forpredicting a motion vector according to the present embodiment, andwhich is decoded by a decoding device.

FIG. 10 shows a first syntax structure that is described in a sliceheader for each slice of a bitstream generated in accordance with thepresent embodiment. The figure shows only syntax elements related to thepresent embodiment. In case that a slice type is a B slice, a flagcollocated_from_l0_flag is established. The flag collocated_from_l0_flagindicates which of the reference pictures a picture colPic of adifferent time uses, namely, a reference picture registered in areference list of L0 or a reference picture registered in a referencelist of L1 of a picture including a prediction block subject toprocessing. The picture colPic of a different time is used when derivinga candidate of a motion vector predictor over time or when deriving amerge candidate. The detail on the flag collocated_from_l0_flag will bedescribed later.

The syntax elements described above may be established in a pictureparameter set that describes a syntax element that is set for eachpicture.

FIG. 11 shows a syntax pattern described for each prediction block. Incase that the value of the prediction mode PredMode of a predictionblock is inter prediction (MODE_INTER), merge_flag[x0][y0] thatindicates whether or not a mode is a merge mode is established. x0 andy0 are indexes indicating the position of an upper left pixel in aprediction block in a picture of brightness signals, andmerge_flag[x0][y0] is a flag indicating whether or not the mode of aprediction block positioned at (x0, y0) in the picture is a merge modeor not.

Next, in case that merge_flag[x0][y0] is 1, which indicates that themode is a merge mode, a syntax element merge_idx[x0][y0] of an index ofa merge list, which is a list of merge candidates to be referred to, isestablished. x0 and y0 are indexes indicating the position of an upperleft pixel in a prediction block in a picture, and merge_flag[x0][y0] isa merge index of a prediction block positioned at (x0, y0) in thepicture. FIG. 12 shows an example of an entropy code of a syntax elementmerge_idx[x0][y0] of a merge index. According to the present embodiment,the number of candidates of merge is set to 5. When the merge index is0, 1, 2, 3, and 4, the code of syntax element merge_idx[x0][y0] of amerge index is ‘0’, ‘10’, ‘110’, ‘1110’, and ‘1111’, respectively.

On the other hand, in case that merge_flag[x0][y0] is 0, themerge_flag[x0][y0] indicates that the mode is not a merge mode, and incase that the slice type is a B slice, a syntax elementinter_pred_flag[x0][y0] that identifies an inter prediction mode isestablished. By this syntax element, L0 prediction (Pred_L0), L1prediction (Pred_L1), and bi-prediction (Pred_BI) are distinguished. Foreach L0 and L1, syntax elements of reference index ref_idx_l0[x0][y0]and ref_idx_l1[x0][y0] for specifying a reference picture, and syntaxelements mvd_l0[x0][y0][j] and mvd_l1[x0][y0][j] of a motion vectordifference, which is a difference between a motion vector of aprediction block derived by detection of a motion vector and a motionvector predictor, are established. x0 and y0 are indexes indicating theposition of an upper left pixel in a prediction block in a picture.ref_idx_l0[x0][y0] and mvd_l0[x0][y0][j] are a reference index and amotion vector difference of L0 of a prediction block positioned at (x0,y0) in the picture, respectively. ref_idx_l1[x0][y0], mvd_l1[x0][y0][j]are a reference index and a motion vector difference of L1 of aprediction block positioned at (x0, y0) in the picture, respectively. jindicates components of motion vector difference. A value 0 for jrepresents x component, and a value 1 for j represents y component.Next, syntax elements mvp_idx_l0[x0][y0] and mvp_idx_l1[x0][y0] of indexof a motion vector predictor list, which is a list of candidates ofmotion vector predictor to be referred to, is established. x0 and y0 areindexes indicating the position of an upper left pixel in a predictionblock in a picture. mvp_idx_l0[x0][y0] and mvp_idx_l1[x0][y0] are motionvector predictor index of L0 and L1 of a prediction block positioned at(x0, y0) in the picture. According to the present embodiment, the valueof the number of candidates is set to 2.

A method for deriving inter prediction information according to theembodiment is performed in the inter prediction information derivationunit 104 of the moving picture encoding device of FIG. 1 and in theinter prediction information derivation unit 205 of the moving picturedecoding device of FIG. 2.

Next, an explanation will be given on the method for deriving interprediction information according to an embodiment while referring tofigures. The method for deriving inter prediction information isexecuted for each prediction block that constitutes a coding block atany of the encoding processes or decoding processes. If a predictionmode PredMode of a prediction block is inter prediction (MODE_INTER) anda mode is a merge mode, and in case of encoding, the method is used whenderiving a prediction mode, a reference index, and a motion vector of aprediction block subject to encoding by using a prediction mode, areference index, and a motion vector of an encoded prediction block. Incase of decoding, the method is used when deriving a prediction mode, areference index, and a motion vector of a prediction block subject todecoding by using a prediction mode, a reference index, and a motionvector of a decoded prediction block.

In a merge mode, a merge candidate is derived not only from the fiveprediction blocks (i.e., a prediction block A adjacent to the left, aprediction block B adjacent to the top, a prediction block C adjacent tothe upper right, a prediction block D adjacent to the lower left, and aprediction block E adjacent to the upper left) explained while referringto FIGS. 5, 6, 7, and 8, but also from a prediction block of aprediction block Col (T0 or T1) at an identical position or in aproximity and different in time, which has been explained whilereferring to FIG. 9. The inter prediction information derivation unit104 of the moving picture encoding device and the inter predictioninformation derivation unit 205 of the moving picture decoding deviceregister those merge candidates in merge candidate list in prescribedorder that is common between encoding and decoding. The inter predictioninformation derivation unit 104 of the moving picture encoding devicedetermines a merge index that specifies an element of a candidate listand encodes via a first bitstream generating unit. The inter predictioninformation derivation unit 205 of the moving picture decoding deviceselects a prediction block from the merge candidate list in accordancewith a merge index decoded in the first bitstream decoding unit 202 andprovided, and performs motion compensation prediction by using interprediction information (e.g., a prediction mode, a reference index, amotion vector, or the like) of the selected merge candidate.

FIG. 13 shows a detailed configuration of the inter predictioninformation derivation unit 104 of the moving picture encoding device ofFIG. 1. FIG. 14 shows a detailed configuration of the inter predictioninformation derivation unit 205 of the moving picture decoding device ofFIG. 2.

Portions surrounded by a thick line box in FIGS. 13 and 14 indicate theinter prediction information derivation unit 104 of the moving pictureencoding device and the inter prediction information derivation unit 205of the moving picture decoding device, respectively.

In addition, portions surrounded by a thick dotted line in the boxesindicate a construction unit 120 of merge candidate list of the movingpicture encoding device and a construction unit 220 of merge candidatelist of the moving picture decoding device, respectively. Theconstruction unit of merge candidate list is provided also in the movingpicture decoding device that corresponds to the moving picture encodingdevice according to the embodiment so that same derivation results thatdo not contradict between encoding and decoding can be obtained.

According to the method for deriving inter prediction informationaccording to the embodiment, in merge candidate derivation and in mergecandidate list construction process in the construction unit 120 ofmerge candidate list of the moving picture encoding device and theconstruction unit 220 of merge candidate list of the moving picturedecoding device, it is assumed that merge candidate derivation and mergecandidate list construction process of a prediction block subject toprocessing are performed without referring to a prediction blockincluded in a coding block identical to a coding block including aprediction block subject to processing. In this manner, in case that thepartition mode (PartMode) of a coding block is not 2N by 2N partition(PART_2N×2N), that is, in case that a plurality of prediction blocksexist in a coding block, merge candidate derivation and merge candidatelist construction process of a prediction block subject to processingfor each prediction block can be performed in parallel in a coding blockat encoding.

An explanation will be given for each partition mode (PartMode) on theparallel processes of merge candidate list construction of respectiveprediction block in a coding block while referring to FIG. 15. FIG. 15illustrates a prediction block that is in the proximity of a predictionblock subject to processing for each partition mode (PartMode) of theprediction block subject to processing. In FIG. 15, A0, B0, C0, D0, andE0 indicates: a prediction block A adjacent to the left edge of theprediction block subject to processing of which the partition indexPartIdx is 0; a prediction block B adjacent to the upper edge thereof; aprediction block C adjacent to the upper right vertex thereof; aprediction block D adjacent to the lower left vertex thereof; and aprediction block E adjacent to the upper left vertex thereof,respectively. A1, B1, C1, D1, and E1 indicates: a prediction block Aadjacent to the left edge of the prediction block subject to processingof which the partition index PartIdx is 1; a prediction block B adjacentto the upper edge thereof; a prediction block C adjacent to the upperright vertex thereof; a prediction block D adjacent to the lower leftvertex thereof; and a prediction block E adjacent to the upper leftvertex thereof, respectively. A2, B2, C2, D2, and E2 indicates: aprediction block A adjacent to the left edge of the prediction blocksubject to processing of which the partition index PartIdx is 2; aprediction block B adjacent to the upper edge thereof; a predictionblock C adjacent to the upper right vertex thereof; a prediction block Dadjacent to the lower left vertex thereof; and a prediction block Eadjacent to the upper left vertex thereof, respectively. A3, B3, C3, D3,and E3 indicates: a prediction block A adjacent to the left edge of theprediction block subject to processing of which the partition indexPartIdx is 3; a prediction block B adjacent to the upper edge thereof; aprediction block C adjacent to the upper right vertex thereof; aprediction block D adjacent to the lower left vertex thereof; and aprediction block E adjacent to the upper left vertex thereof,respectively.

FIGS. 15B, 15C, and 15D show prediction blocks in the proximity in casethat a partition mode (PartMode) is 2N by N partition (PART_2N×N), 2N bynU partition (PART_2N×nU), or 2N by nD partition (PART_2N×nD), where acoding block subject to processing is partitioned into two predictionblocks arranged vertically. The prediction block B1 in the proximity ofa prediction block subject to processing of which PartIdx is 1, is aprediction block of which PartIdx is 0. Therefore, merge candidatederivation and merge candidate list construction of a prediction block,of which PartIdx is 1, by referring to the prediction block B1 cannot beprocessed until merge candidate derivation and merge candidate listconstruction process of a prediction block, which is a prediction blockB1 and belongs to a same coding block and of which PartIdx is 0, iscompleted and a merge candidate to be used is specified. Therefore, inthe method for deriving inter prediction information according to theembodiment, in case that a partition mode is 2N by N partition(PART_2N×N), 2N by nU partition (PART_2N×nU), or 2N by nD partition(PART_2N×nD), and in case that PartIdx of a prediction block subject toprocessing is 1, merge candidate derivation and merge candidate listconstruction process of two prediction blocks in the coding block can beprocessed in parallel by referring to coding information of theprediction block A1, C1, D1, or E1, which are not included in a codingblock identical to a coding block including the prediction block subjectto processing, and by performing merge candidate derivation and mergecandidate list construction process of a prediction block of whichPartIdx is 1, without referring to coding information of the predictionblock B1, which is a prediction block adjacent to the upper edge of theprediction block subject to processing, and is included in a codingblock identical to a coding block including the prediction block subjectto processing, and of which PartIdx is 0.

FIGS. 15F, 15F, and 15G show prediction blocks in the proximity in casethat a partition mode (PartMode) is N by 2N partition (PART_N×2N), nL by2N partition (PART_nL×2N), or nR by 2N partition (PART_nR×2N), where acoding block subject to processing is partitioned into two predictionblocks arranged horizontally. The prediction block A1 in the proximityof a prediction block subject to processing, of which PartIdx is 1, is aprediction block of which PartIdx is 0. Therefore, merge candidatederivation and merge candidate list construction of a prediction block,of which PartIdx is 1, by referring to the prediction block A1 cannot beprocessed until merge candidate derivation and merge candidate listconstruction process of a prediction block, which is a prediction blockA1 and belongs to a same coding block and of which PartIdx is 0, iscompleted and a merge candidate to be used is specified. Therefore, inthe method for deriving inter prediction information according to theembodiment, in case that a partition mode is N by 2N partition(PART_N×2N), nL by 2N partition (PART_nL×2N), and nR by 2N partition(PART_nR×2N), and in case that PartIdx of a prediction block subject toprocessing is 1, merge candidate derivation and merge candidate listconstruction process of respective prediction blocks in the coding blockcan be processed in parallel by referring to coding information of theprediction block B1, C1, D1, or E1, which are not included in a codingblock identical to a coding block including the prediction block subjectto processing, and by performing merge candidate derivation and mergecandidate list construction process of a prediction block of whichPartIdx is 1, without referring to coding information of the predictionblock A1, which is a prediction block adjacent to the left edge of theprediction block subject to processing, and is included in a codingblock identical to a coding block including the prediction block subjectto processing, and of which PartIdx is 0.

An explanation will be given on the parallel processing of mergecandidate derivation and merge candidate list construction process. FIG.16 shows a flowchart illustrating merge candidate derivation and mergecandidate list construction process by sequential processing, and FIG.17 shows a flowchart illustrating merge candidate derivation and mergecandidate list construction process by parallel processing.

In the sequential processing of merge candidate derivation and mergecandidate list construction process shown in FIG. 16, merge candidate isderived and merge candidate list is constructed for a prediction block,of which a partition index PartIdx is 0, of a coding block subject toprocessing (step S101). Next, in case that the partition mode (PartMode)is 2N by 2N partition (PART_2N×2N) (NO in step S102), the mergecandidate derivation and merge candidate list construction process iscompleted. In case that the partition mode (PartMode) is not 2N by 2Npartition (PART_2N×2N) (NO in step S102), that is, in case that thepartition mode (PartMode) is the 2N by N partition (PART_2N×N), the 2Nby nU partition (PART_2N×nU), the 2N by nD partition (PART_2N×nD), the Nby 2N partition (PART_N×2N), the nL by 2N partition (PART_nL×2N), or thenR by 2N partition (PART_nR×2N), merge candidate is derived and mergecandidate list is constructed for a prediction block, of which apartition index PartIdx is 1, of a coding block subject to processing(step S103), and the merge candidate derivation and merge candidate listconstruction process is completed, accordingly.

In the parallel processing of merge candidate derivation and mergecandidate list construction process shown in FIG. 17, merge candidate isderived and merge candidate list is constructed for a prediction block,of which a partition index PartIdx is 0, of a coding block subject toprocessing (step S101). In parallel with the step S101, in case that thepartition mode (PartMode) is not 2N by 2N partition (PART_2N×2N) (NO instep S102), that is, in case that the partition mode (PartMode) is the2N by N partition (PART_2N×N), the 2N by nU partition (PART_2N×nU), the2N by nD partition (PART_2N×nD), the N by 2N partition (PART_N×2N), thenL by 2N partition (PART_nL×2N), or the nR by 2N partition (PART_nR×2N),merge candidate is derived and merge candidate list is constructed for aprediction block, of which a partition index PartIdx is 1, of a codingblock subject to processing (step S103).

In the parallel processing of merge candidate derivation and mergecandidate list construction process shown in FIG. 17, in case that thepartition mode (PartMode) is the 2N by N partition (PART_2N×N), the 2Nby nU partition (PART_2N×nU), the 2N by nD partition (PART_2N×nD), the Nby 2N partition (PART_N×2N), the nL by 2N partition (PART_nL×2N), or thenR by 2N partition (PART_nR×2N), merge candidate derivation and mergecandidate list construction process of two prediction blocks, of which apartition index PartIdx are 0 and 1 respectively, can be startedsimultaneously, by performing merge candidate derivation and mergecandidate list construction for a prediction block, of which a partitionindex PartIdx is 1, without referring to a prediction block, of which apartition index PartIdx is 0, in the same coding block.

Also in the sequential processing of merge candidate derivation andmerge candidate list construction process shown in FIG. 16, mergecandidate derivation and merge candidate list construction process of aprediction block, of which a partition index PartIdx is 1, can beperformed without referring to a prediction block, of which a partitionindex PartIdx is 0.

Although it is assumed that N by N partition (PART_N×N) is not definedas a partition mode (PartMode) according to the present embodiment, itis also possible to define the N by N partition (PART_N×N). FIG. 15Hshows prediction blocks in the proximity in case that the partition mode(PartMode) is N by N partition (PART_N×N) in which a brightness signalof a coding block subject to processing is partitioned into four blocksvertically and horizontally. The prediction block B1 in the proximity ofa prediction block subject to processing, of which PartIdx is 1, is aprediction block of which PartIdx is 0. Therefore, merge candidatederivation and merge candidate list construction of a prediction block,of which PartIdx is 1, by referring to the prediction block A1 cannot beprocessed until merge candidate derivation and merge candidate listconstruction process of a prediction block, which is a prediction blockA1 and belongs to a same coding block and of which PartIdx is 0, iscompleted and a merge candidate to be used is specified. Therefore, inthe method for deriving inter prediction information according to theembodiment, in case that a partition mode is N by N partition(PART_N×N), and in case that PartIdx of a prediction block subject toprocessing is 1, merge candidate derivation and merge candidate listconstruction process of respective prediction blocks in the coding blockcan be processed in parallel by performing merge candidate derivationand merge candidate list construction process of a prediction block ofwhich PartIdx is 1, without referring to coding information of theprediction block A1, of which PartIdx is 0. The prediction block B2 inthe proximity of a prediction block subject to processing of whichPartIdx is 2, is a prediction block of which PartIdx is 0, and theprediction block C2 is a prediction block of which PartIdx is 1.Therefore, merge candidate derivation and merge candidate listconstruction of a prediction block, of which PartIdx is 2, by referringto the prediction blocks B2 and C2 cannot be processed until mergecandidate derivation and merge candidate list construction process ofprediction blocks, which are prediction blocks B2 and C2 and belong tothe same coding block and of which PartIdx are 0 and 1 respectively, iscompleted and a merge candidate to be used is specified. Therefore, inthe method for deriving inter prediction information according to theembodiment, in case that a partition mode is N by N partition(PART_N×N), and in case that PartIdx of a prediction block subject toprocessing is 2, merge candidate derivation and merge candidate listconstruction process of respective prediction blocks in the coding blockcan be processed in parallel by performing merge candidate derivationand merge candidate list construction process of a prediction block ofwhich PartIdx is 2, without referring to coding information of theprediction blocks B2 and C2, of which PartIdx are 0 and 1, respectively.The prediction block E3 in the proximity of a prediction block subjectto processing of which PartIdx is 3, is a prediction block of whichPartIdx is 0, the prediction block B3 is a prediction block of whichPartIdx is 1, and the prediction block A3 is a prediction block of whichPartIdx is 2. Therefore, merge candidate derivation and merge candidatelist construction of a prediction block, of which PartIdx is 3, byreferring to the prediction blocks E3, B3, and A3 cannot be processeduntil merge candidate derivation and merge candidate list constructionprocess of prediction blocks, which are prediction blocks E3, B3, and A3and belong to the same coding block and of which PartIdx are 0, 1 and 2respectively, is completed and a merge candidate to be used isspecified. Therefore, in the method for deriving inter predictioninformation according to the embodiment, in case that a partition modeis N by N partition (PART_N×N), and in case that PartIdx of a predictionblock subject to processing is 3, merge candidate derivation and mergecandidate list construction process of respective prediction blocks inthe coding block can be processed in parallel by performing mergecandidate derivation and merge candidate list construction process of aprediction block of which PartIdx is 3, without referring to codinginformation of the prediction blocks E3, B3, and A3, of which PartIdxare 0, 1, and 2, respectively.

The inter prediction information derivation unit 104 in FIG. 13 includesa spatial merge candidate generating unit 130, a reference indexderivation unit 131, a time merge candidate generating unit 132, a mergecandidate registering unit 133, a merge candidate identificationdetermining unit 134, a merge candidate supplementing unit 135, and acoding information selection unit 136.

The inter prediction information derivation unit 205 in FIG. 14 includesa spatial merge candidate generating unit 230, a reference indexderivation unit 231 of time merge candidate, a time merge candidategenerating unit 232, a merge candidate registering unit 233, a mergecandidate identification determining unit 234, a merge candidatesupplementing unit 235, and a coding information selection unit 236.

FIG. 18 shows a flowchart illustrating a procedure of a merge candidatederivation and merge candidate list construction process, that is afunction common to the inter prediction information derivation unit 104of the moving picture encoding device and the inter predictioninformation derivation unit 205 of the moving picture decoding deviceaccording to an embodiment of the invention. An explanation on theprocesses will be given below sequentially. Although an explanationwhere a slice type slice_type is a B slice is given in the followingexplanation, the explanation can be also applied to the case of P slice,unless otherwise noted. However, in case that the slicetype slice_typeis a P slice, an inter prediction mode only includes L0 prediction(Pred_L0) and does not include L1 prediction (Pred_L1) nor bi-prediction(Pred_BI). Therefore a process regarding L1 can be omitted.

In the spatial merge candidate generating unit 130 of the interprediction information derivation unit 104 of the moving pictureencoding device and in the spatial merge candidate generating unit 230of the inter prediction information derivation unit 205 of the movingpicture decoding device, spatial merge candidates A, B, C, D, and E fromrespective prediction blocks A, B, C, D, and E in the proximity of ablock subject to encoding or decoding are derived and outputted. N thatindicates A, B, C, D, E, or a spatial merge candidate Col is defined. Aflag availableFlagN indicating whether or not inter predictioninformation of a prediction block N is available as a spatial mergecandidate N, a reference index refIdxL0N of L0 and a reference indexrefIdxL1N of L1 of the spatial merge candidate N, a prediction flagpredFlagL0N indicating whether or not the L0 prediction is performed anda prediction flag predFlagL1N indicating whether or not the L1prediction is performed, a motion vector mvL0N of L0, and a motionvector mvL1N of L1 are outputted (step S201). However, according to thepresent embodiment, since a merge candidate is derived without referringto a prediction block included in a coding block identical to the codingblock that includes a prediction block subject to processing, a spatialmerge candidate included in the coding block identical to the codingblock including a prediction block subject to processing is not derived.A detailed explanation will be given later on the detailed processingprocedure of step S201 with reference to the flowchart shown in FIG. 19.

Subsequently, in the reference index derivation unit 131 of time mergecandidate of the inter prediction information derivation unit 104 of themoving picture encoding device and in the reference index derivationunit 231 of time merge candidate of the inter prediction informationderivation unit 205 of the moving picture decoding device, a referenceindex of a time merge candidate is derived from a prediction block inthe proximity of a block subject to encoding or decoding are derived andoutput (step S202). However, according to the present embodiment, areference index of a time merge candidate is derived without referringto a prediction block included in a coding block identical to the codingblock that includes a prediction block subject to processing. In casethat a slice type slice_type is a P slice and inter prediction isperformed by using inter prediction information of the time mergecandidate, only the reference index of L0 is derived in order to performL0 prediction (Pred_L0). In case that a slice type slice_type is a Bslice and inter prediction is performed by using inter predictioninformation of the time merge candidate, respective reference indexes ofL0 and L1 are derived in order to perform bi-prediction (Pred_BI). Adetailed explanation will be given later on the detailed processingprocedure of step S202 with reference to the flowcharts shown in FIG.21, FIG. 23, FIG. 25, FIG. 27, FIG. 29, FIG. 30, and FIG. 32.

Subsequently, in the time merge candidate generating unit 132 of theinter prediction information derivation unit 104 of the moving pictureencoding device and in the time merge candidate generating unit 232 ofthe inter prediction information derivation unit 205 of the movingpicture decoding device, a time merge candidate is derived from apicture of a different time and the time merge candidate is outputted. Aflag availableFlagCol indicating whether or not a time merge candidateis available, a prediction flag predFlagL0Col indicating whether or notthe L0 prediction of time merge candidate is performed and a predictionflag predFlagL1Col indicating whether or not the L1 prediction isperformed, a motion vector mvL0N of L0, and a motion vector mvL1N of L1are outputted (step S203). A detailed explanation will be given later onthe detailed processing procedure of step S203 with reference to theflowchart shown in FIG. 34.

Subsequently, in the merge candidate registering unit 133 of the interprediction information derivation unit 104 of the moving pictureencoding device and in the merge candidate registering unit 233 of theinter prediction information derivation unit 205 of the moving picturedecoding device, a merge candidate list is generated, and spatial mergecandidates A, B, C, D, and E, and a time merge candidate Col are addedto the merge candidate list mergeCandList, by which, the merge candidatelist mergeCandList is established, and the merge candidate listmergeCandList is outputted (step S204). A detailed explanation will begiven later on the detailed processing procedure of step S204 withreference to the flowchart shown in FIG. 41.

Subsequently, in the merge candidate identification determining unit 134of the inter prediction information derivation unit 104 of the movingpicture encoding device and in the merge candidate identificationdetermining unit 234 of the inter prediction information derivation unit205 of the moving picture decoding device, a merge candidate list isgenerated, in case that motion vectors of reference indexes of anidentical merge candidate have a same value in the merge candidate listmergeCandList, the merge candidate is omitted except for a mergecandidate that is earliest in the order, and the merge candidate listmergeCandList is outputted (step S205).

Subsequently, in the merge candidate supplementing unit 135 of the interprediction information derivation unit 104 of the moving pictureencoding device and in the merge candidate supplementing unit 235 of theinter prediction information derivation unit 205 of the moving picturedecoding device, a merge candidate list is supplemented so that thenumber of merge candidates registered in the merge candidate listmergeCandList, and the merge candidate list mergeCandList is outputted(step S206). According to the present embodiment, the number of mergecandidates is set to 5.

While the upper limit of the number of merge candidates registered inthe merge candidate list mergeCandList is set to 5, a merge candidate ofwhich the prediction mode is bi-prediction (Pred_BI) and which is madeby changing the combination of L0 prediction and L1 prediction betweenmerge candidates that have been registered already; a merge candidate ofwhich the prediction mode is bi-prediction (Pred_BI), which has adifferent reference index, and the value of the motion vector of whichis (0, 0); or the like is added.

A detailed explanation will be given on a method for deriving a mergecandidate N from a prediction block N in the proximity of a predictionblock subject to encoding or decoding, which is a processing procedureof step S201 of FIG. 18. FIG. 19 shows a flowchart illustratingprocedure of spatial merge candidate derivation process of step S201 inFIG. 18. N represents A (left), B (up), C (upper right), D (lower left),or E (upper left) indicating an are of a prediction block in theproximity. According to the present embodiment, up to four spatial mergecandidates are derived from five prediction blocks in the proximity.

In FIG. 18, by assigning A as a parameter N, coding information of aprediction block A adjacent to the left edge of a prediction blocksubject to encoding or decoding is checked and a merge candidate A isderived, by assigning B as a parameter N, coding information of aprediction block B adjacent to the upper edge is checked and a mergecandidate B is derived, by assigning C as a parameter N, codinginformation of a prediction block C adjacent to the upper right ischecked and a merge candidate C is derived, by assigning D as aparameter N, coding information of a prediction block D adjacent to thelower left is checked and a merge candidate D is derived, and byassigning E as a parameter N, coding information of a prediction block Eadjacent to the upper left is checked and a merge candidate E is derived(step S1101-step S1114).

First, in case that the parameter N is E, and that values of a flagsavailableFlagA, availableFlagB, availableFlagC, and availableFlagD areadded and the total thereof is 4 (YES in S1102), that is, in case thatfour spatial merge candidates are derived, a flag of a merge candidate EavailableFlagE is set to 0 (step S1107), both values of motion vectorsmvL0E and mvL1E of merge candidate E are set to (0,0) (step S1108), bothvalues of flags predFlagL0E and predFlagL1E of merge candidate E are setto 0 (step S1109), and this spatial merge candidate derivation processis completed. According to the present embodiment, up to four spatialmerge candidate are derived from prediction blocks in the proximity.Therefore, in case that four spatial merge candidates have been derivedalready, it is not required to perform the derivation process of spatialmerge candidates any more.

On the other hand, in case that the parameter N is not E, or in casethat values of a flags availableFlagA, availableFlagB, availableFlagC,and availableFlagD are added and the total thereof is not 4 (NO inS1102), the method proceeds to step S1103. If the prediction block N inthe proximity is included in a coding block identical to a coding blockincluding a prediction block subject to derivation (YES in step S1103),the value of a flag availableFlagN of a merge candidate N is set to 0(step S1107), both values of motion vectors mvL0N and mvL1N of the mergecandidate N are set to (0,0) (step S1108), and both values of flagspredFlagL0N and predFlagL1N of the merge candidate N are set to 0 (stepS1109). If the prediction block N in the proximity is included in acoding block identical to a coding block including a prediction blocksubject to derivation (YES in step S1103), the value of a flagavailableFlagN of merge candidate N is set to 0 (step S1107), by notreferring to coding information of the prediction block N in theproximity and by setting the value of flag availableFlagN of the mergecandidate N to 0, so as not to using as a spatial merge candidate, mergecandidate derivation and merge candidate list construction process forrespective prediction blocks in a same coding block can be processed inparallel.

More specifically, the case of prediction block B adjacent to the upperedge of a prediction block subject to derivation, where a partition modeis 2N by N partition (PART_2N×N), 2N by nU partition (PART_2N×nU), or 2Nby nD partition (PART_2N×nD) and where that PartIdx of a predictionblock subject to processing is 1, corresponds to the case where theprediction block N in the proximity is included in a coding blockidentical to a coding block including a prediction block subject toderivation. In this case, the prediction block B adjacent to the upperedge of a prediction block subject to derivation is a prediction blockwhich is included in a coding block identical to a coding blockincluding a prediction block subject to derivation and of which thePartIdx is 0. Therefore, by not referring to coding information of theprediction block B in the proximity and by setting the value of flagavailableFlagB of the merge candidate B to 0 so as not to using as aspatial merge candidate, merge candidate derivation and merge candidatelist construction process for respective prediction blocks in a samecoding block can be processed in parallel.

Further, the case of a prediction block A adjacent to the upper edge ofa prediction block subject to derivation, where a partition mode is N by2N partition (PART_N×2N), nL by 2N partition (PART_nL×2N), or nR by 2Npartition (PART_nR×2N) and where PartIdx of a prediction block subjectto processing is 1, also corresponds to the case where the predictionblock N in the proximity is included in a coding block identical to acoding block including a prediction block subject to derivation. Also inthis case, the prediction block A adjacent to the left edge of aprediction block subject to derivation is a prediction block which isincluded in a coding block identical to a coding block including aprediction block subject to derivation and of which the PartIdx is 0.Therefore, by not referring to coding information of the predictionblock A in the proximity and by setting the value of flag availableFlagAof the merge candidate A to 0 so as not to using as a spatial mergecandidate, merge candidate derivation and merge candidate listconstruction process for respective prediction blocks in a same codingblock can be processed in parallel.

Although not defined according to the present embodiment, also in casethat a partition mode (PartMode) is N by N partition (PART_N×N), and incase that PartIdx of a prediction block subject to processing is 1, 2,or 3, the prediction block N in the proximity is sometimes included in acoding block identical to a coding block including a prediction blocksubject to derivation.

On the other hand, in case that the prediction block N in the proximityis not included in a coding block identical to a coding block includinga prediction block subject to derivation (YES in step S1103), theprediction block N in the proximity of a prediction block subject toencoding or decoding is specified, and in case that respectiveprediction blocks N are available, coding information of a predictionblock N is derived from the coding information storing memory 115 orfrom the coding information storing memory 210 (step S1104).

If the prediction block N in the proximity cannot be used (NO in stepS1105), or the prediction mode PredMode of the prediction block N isintra prediction (MODE_INTRA) (YES in step S1106), the value of a flagavailableFlagN of a merge candidate N is set to 0 (step S1107), bothvalues of motion vectors mvL0N and mvL1N of the merge candidate N areset to (0,0) (step S1108), and both values of flags predFlagL0N andpredFlagL1N of the merge candidate N are set to 0 (step S1109). The casewhere a prediction block N in the proximity cannot be used corresponds,for example, to a case where the prediction block N in the proximity ispositioned outside of a slice subject to encoding or decoding, a casewhere encoding or decoding process has not been completed because theblock N is late in the processing order of encoding or decoding process,etc.

On the other hand, if the prediction block N in the proximity is outsideof a coding block identical to a coding block including a predictionblock subject to derivation (YES in step S1104), the prediction block Nin the proximity is available (YES in step S1105), and in case that theprediction mode PredMode of the prediction block N is not an intraprediction (MODE_INTRA) (YES in step S1106), the inter predictioninformation of the prediction block N is used as the inter predictioninformation of the merge candidate N. The value of a flag availableFlagNof the merge candidate N is set to 1 (step S1110), the motion vectorsmvL0N and mvL1N of the merge candidate N are set to a value identical tothat of the motion vectors mvL0N[xN][yN] and mvL1N[xN][yN] of respectiveprediction block N (step S1111), the reference indexes refIdxL0N andrefIdxL1N of the merge candidate N are set to a value identical to thatof the reference indexes refIdxL0[xN][yN] and refIdxL1[xN][yN] ofrespective prediction block N (step S1112), and flags predFlagL0N andpredFlagL1N of a merge candidate N are set to flags predFlagL0[xN][yN]and predFlagL1[xN][yN] of respective prediction block N (step S1113). xNand yN are indexes indicating the position of an upper left pixel in aprediction block N in a picture.

The above process of steps S1102 through S1113 are repeated for N=A, B,C, D, and E, respectively (step S1101-step S1114).

Next, a detailed explanation will be given on a method for deriving areference index of a time merge candidate of step S202 in FIG. 18.Respective reference indexes of L0 and L1 of a time merge candidate arederived.

According to the present embodiment, reference indexes of a time mergecandidate is derived by using a reference index of a spatial mergecandidate, that is, a reference index used in a prediction block in theproximity of a prediction block subject to encoding or decoding. This isbecause, in case that a time merge candidate is selected, a referenceindex of a prediction block subject to encoding or decoding has a highcorrelation with the reference index of a prediction block in theproximity of a prediction block subject to encoding or decoding, whichwill be a spatial merge candidate. Particularly, according to thepresent embodiment, only a reference index of a prediction block Aadjacent to the left edge of the prediction block subject to derivation,or a prediction block B adjacent to the upper edge thereof is used,except for a sixth exemplary embodiment and a seventh exemplaryembodiment, which will be described later. This is because, theprediction blocks A and B adjacent to the edge of the prediction blocksubject to encoding or decoding, among the prediction blocks A,B,C,D,and E in the proximity, which are also a spatial merge candidates, havea higher correlation than the prediction blocks C,D, and E adjacent onlyto a vertex. By limiting prediction blocks to use to prediction blocks Aand B without using the prediction blocks C, D, and E having relativelylow correlation, an improvement effect of encoding efficiency can beobtained by deriving a reference index of a time merge candidate, andthe amount of calculation and a frequency of access to memory relatingto derivation process of a reference index of a time merge candidate canbe reduced.

First Exemplary Embodiment

An explanation will be given below on the present embodiment with someexemplary embodiments. First, an explanation will be given below on afirst exemplary embodiment of the present embodiment. FIG. 20 shows anadjacent block referred to in the derivation process of a referenceindex of a time merge candidate according to the first exemplaryembodiment of the present embodiment. According to the first exemplaryembodiment of the present embodiment, in accordance with the partitionmode (PartMode), which of prediction blocks: a prediction block adjacentto the left edge of a prediction block subject to derivation, or aprediction block adjacent to the upper edge thereof is used is switched.A prediction block adjacent to the edge outside of a coding block isreferred to. In case that a partition mode (PartMode) is 2N by 2Npartition (PART_2N×2N), as shown in FIG. 20A, a prediction block A0adjacent to the left of a prediction block subject to derivation isreferred to, and a reference index of LX of a time merge candidate isset to a value of reference index of LX of the prediction block A0.

In case that a partition mode (PartMode) is 2N by N partition(PART_2N×N), 2N by nU partition (PART_2N×nU), or 2N by nD partition(PART_2N×nD), where coding block subject to processing is partitionedinto two prediction blocks arranged vertically, as shown in FIGS. 20B,20C, and 20D, prediction blocks adjacent to the left edge of respectiveprediction blocks subject to derivation are referred to, and respectivereference indexes of LX of time merge candidates are set to values ofreference indexes of LX of prediction blocks adjacent to the left edgeof respective prediction blocks subject to derivation. In case of aprediction block subject to derivation of which the partition indexPartIdx is 0, a prediction block A0 adjacent to the left is referred to,and a reference index of LX of a time merge candidate is set to a valueof reference index of LX of the prediction block A0. In case of aprediction block subject to derivation of which the partition indexPartIdx is 1, a prediction block A1 adjacent to the left is referred to,and a reference index of LX of a time merge candidate is set to thevalue of reference index of LX of the prediction block A1. Since bothprediction blocks A0 and A1 to refer to are outside of the coding block,a reference index of time merge candidate of two prediction blocks, ofwhich the partition index PartIdx are 0 and 1 respectively, can bederived in parallel, respectively.

In case that a partition mode (PartMode) is N by 2N partition(PART_N×2N), nL by 2N partition (PART_nL×2N), or nR by 2N partition(PART_nR×2N), where coding block subject to processing is partitionedinto two prediction blocks arranged horizontally, as shown in FIGS. 20E,20F, and 20G, a prediction block adjacent to the upper edge of aprediction block subject to derivation is referred to, and respectivereference indexes of LX of time merge candidates are set to values ofreference indexes of LX of prediction blocks adjacent to the upper edgeof respective prediction blocks subject to derivation. In case of aprediction block subject to derivation of which the partition indexPartIdx is 0, a prediction block B0 adjacent to the top is referred to,and a reference index of LX of a time merge candidate is set to a valueof reference index of LX of the prediction blocks B0 and/or B1. In caseof a prediction block subject to derivation of which the partition indexPartIdx is 1, a prediction block B1 adjacent to the top is referred to,and a reference index of LX of a time merge candidate is set to thevalue of the reference index of LX of the prediction block B1. Sinceboth prediction blocks B0 and B1 to refer to are outside of the codingblock, a reference index of time merge candidate of two predictionblocks, of which the partition index PartIdx are 0 and 1 respectively,can be derived in parallel, respectively.

However, in case that prediction blocks A and B in the proximity do notperform LX prediction, a reference index of LX of a time merge candidateis set to a default value 0. The reason why the default value of areference index of LX of a time merge candidate is set to 0 in case thatprediction blocks A and B in the proximity do not perform LX predictionis that a reference picture corresponding to the reference index value 0has the highest possibility to be selected in inter prediction. However,the scope of the present invention is not limited to this example. Thedefault value of the reference index may be set to a value other than 0(e.g., 1, 2, etc.), or a syntax element indicating the default value ofthe reference index may be provided in a bitstream at a sequence level,at a picture level, or at a slice level, so that the syntax element canbe transmitted and selected at encoding.

FIG. 21 shows a flowchart illustrating procedure of derivation processof a reference index of a time merge candidate in step S202 of FIG. 18according to the first exemplary embodiment of the present embodiment.First, in case that the partition mode (PartMode) is not N by 2Npartition (PART_N×2N), nL by 2N partition (PART_nL×2N), or nR by 2Npartition (PART_nR×2N) (NO in step S2101), that is, in case of 2N by 2Npartition (PART_2N×2N), 2N by N partition (PART_2N×N), 2N by nUpartition (PART_2N×nU), 2N by nD partition (PART_2N×nD), codinginformation of a prediction block A adjacent to the left is derived fromthe coding information storing memory 115 or 210 (step S2111).

Subsequent processes of step S2113 through step S2115 are performed forL0 and L1 respectively (step S2112-S2116). In case of deriving areference index of L0 of a time merge candidate, LX is set to L0, and incase of deriving a reference index of L1, LX is set to L1. However, incase that the slice type slice_type is a P slice, an inter predictionmode only includes L0 prediction (Pred_L0) and does not include L1prediction (Pred_L1) nor bi-prediction (Pred_BI). Therefore a processregarding L1 can be omitted.

In case that a flag predFlagLX[xA][yA] indicating whether or not toperform LX prediction of a prediction block A is not 0 (YES in stepS2113), a reference index refIdxLXCol of LX of a time merge candidate isset to a value identical to the value of reference indexrefIdxLX[xA][yA] of LX of the prediction block A (step S2114). xA and yAare indexes indicating the position of an upper left pixel in aprediction block A in a picture.

According to the present embodiment, in prediction block N (N=A, B), incase that the prediction block N is outside a slice subject to encodingand decoded and cannot be used, in case that the prediction block N hasnot been encoded because the prediction block N is subsequent to theprediction block subject to encoding or decoding in the order ofencoding or decoding so that the prediction block N cannot be used, orin case that the prediction mode PredMode is intra prediction(MODE_INTRA), both flags, predFlagL0[xN][yN] indicating whether or notto use L0 prediction and predFlagL1[xN][yN] indicating whether or not touse L1 prediction, are 0. xN and yN are indexes indicating the positionof an upper left pixel in a prediction block N in a picture. In casethat the prediction mode PredMode of the prediction block N is interprediction (MODE_INTER) and the inter prediction mode is L0 prediction(Pred_L0), the flag predFlagL0[xN][yN] indicating whether or not to useL0 prediction of the prediction block N is 1, and the flagpredFlagL1[xN][yN] indicating whether or not to use L1 prediction is 0.In case that the inter prediction mode of the prediction block N is L1prediction (Pred_L1), the flag predFlagL0[xN][yN] indicating whether ornot to use L0 prediction of the prediction block N is 0, and the flagpredFlagL1[xN][yN] indicating whether or not to use L1 prediction is 1.In case that the inter prediction mode of the prediction block N isbi-prediction (Pred_BI), the flag predFlagL0[xN][yN] indicating whetheror not to use L0 prediction of the prediction block N and the flagpredFlagL1[xN][yN] indicating whether or not to use L1 prediction areboth 1.

In case that a flag predFlagLX[xA][yA] indicating whether or not toperform LX prediction of a prediction block A is 0 (NO in step S2113), areference index refIdxLXCol of LX of a time merge candidate is set to adefault value 0 (step S2115).

Processes of step S2113 through step S2115 are performed for L0 and L1respectively (step S2112-S2116), and the derivation process of areference index is completed.

On the other hand, in case that the partition mode (PartMode) is N by 2Npartition (PART_N×2N), nL by 2N partition (PART_nL×2N), or nR by 2Npartition (PART_nR×2N) (YES in step S2101), coding information of aprediction B adjacent to the top of the prediction block subject toderivation, is derived from the coding information storing memory 115 or210 (step S2117).

Subsequent processes of step S2119 through step S2121 are performed forL0 and L1 respectively (step S2118-S2122). In case of deriving areference index of L0 of a time merge candidate, LX is set to L0, and incase of deriving a reference index of L1, LX is set to L1. However, incase that the slice type slice_type is a P slice, an inter predictionmode only includes L0 prediction (Pred_L0) and does not include L1prediction (Pred_L1) nor bi-prediction (Pred_BI). Therefore a processregarding L1 can be omitted.

In case that a flag predFlagLX[xB][yB] indicating whether or not toperform LX prediction of a prediction block B is not 0 (YES in stepS2119), a reference index refIdxLXCol of LX of a time merge candidate isset to a value identical to the value of reference indexrefIdxLX[xB][yB] of LX of the prediction block B (step S2120). xB and yBare indexes indicating the position of an upper left pixel in aprediction block B in a picture.

In case that a flag predFlagLX[xB][yB] indicating whether or not toperform LX prediction of a prediction block B is 0 (NO in step S2119), areference index refIdxLXCol of LX of a time merge candidate is set to adefault value 0 (step S2121).

Processes of step S2119 through step S2121 are performed for L0 and L1respectively (step S2118-S2122), and the derivation process of thereference index is completed.

Second Exemplary Embodiment

Next, an explanation will be given below on a second exemplaryembodiment of the present embodiment. FIG. 22 shows adjacent blocksreferred to in the derivation process of a reference index of a timemerge candidate according to the second exemplary embodiment of thepresent embodiment. According to the second exemplary embodiment of thepresent embodiment, in accordance with the partition mode (PartMode) ofa prediction block and the partition index PartIdx of the predictionblock, which of prediction blocks: a prediction block adjacent to theleft edge of a prediction block subject to derivation; or a predictionblock adjacent to the upper edge thereof is used is switched. Aprediction block adjacent to the edge outside of a coding block isreferred to. In case that a partition mode (PartMode) is 2N by 2Npartition (PART_2N×2N), as shown in FIG. 22A, a prediction block A0adjacent to the left of a prediction block subject to derivation isreferred to, and a reference index of LX of a time merge candidate isset to a value of reference index of LX of the prediction block A0.

In case that a partition mode (PartMode) is 2N by N partition(PART_2N×N), 2N by nU partition (PART_2N×nU), or 2N by nD partition(PART_2N×nD), where coding block subject to processing is partitionedinto two prediction blocks arranged vertically, as shown in FIGS. 22B,20C, and 20D, prediction blocks adjacent to the left edge of respectiveprediction blocks subject to derivation are referred to, and respectivereference indexes of LX of time merge candidates are set to values ofreference indexes of LX of prediction blocks adjacent to the left edgeof respective prediction blocks subject to derivation. In case of aprediction block subject to derivation of which the partition indexPartIdx is 0, a prediction block A0 adjacent to the left is referred to,and a reference index of LX of a time merge candidate is set to a valueof reference index of LX of the prediction block A0. In case of aprediction block subject to derivation of which the partition indexPartIdx is 1, a prediction block A1 adjacent to the left is referred to,and a reference index of LX of a time merge candidate is set to thevalue of reference index of LX of the prediction block A1. Since bothprediction blocks A0 and A1 to refer to are outside of the coding block,a reference index of time merge candidate of two prediction blocks, ofwhich the partition index PartIdx are 0 and 1 respectively, can bederived in parallel, respectively.

In case that a partition mode (PartMode) is N by 2N partition(PART_N×2N), nL by 2N partition (PART_nL×2N), or nR by 2N partition(PART_nR×2N), where coding block subject to processing is partitionedinto two prediction blocks arranged horizontally, as shown in FIGS. 22E,22F, and 22G, a prediction block A0 adjacent to the left is referred tofor a prediction block subject to derivation of which the partitionindex PartIdx is 0, reference indexes of LX of time merge candidates areset to a value of reference index of LX of prediction block A0. In caseof a prediction block subject to derivation of which the partition indexPartIdx is 1, a prediction block B1 adjacent to the top is referred to,and a reference index of LX of a time merge candidate is set to thevalue of the reference index of LX of the prediction block B1. Sinceboth prediction blocks A0 and B1 to refer to are outside of the codingblock, a reference index of time merge candidate of two predictionblocks of which the partition index PartIdx are 0 and 1 respectively,can be derived in parallel, respectively.

However, in case that prediction blocks A and B in the proximity do notperform LX prediction, a reference index of LX of a time merge candidateis set to a default value 0. The reason why the default value of areference index of LX of a time merge candidate is set to 0 in case thatprediction blocks A and B in the proximity do not perform LX predictionis that a reference picture corresponding to the reference index value 0has the highest possibility to be selected in inter prediction. However,the scope of the present invention is not limited to this example. Thedefault value of the reference index may be set to a value other than 0(e.g., 1, 2, etc.), or a syntax element indicating the default value ofthe reference index may be provided in a bitstream at a sequence level,at a picture level, or at a slice level, so that the syntax element canbe transmitted and selected at encoding.

FIG. 23 shows a flowchart illustrating procedure of derivation processof a reference index of a time merge candidate in step S202 of FIG. 18according to the second exemplary embodiment of the present embodiment.First, in case that the partition mode (PartMode) is not N by 2Npartition (PART_N×2N), nL by 2N partition (PART_nL×2N), or nR by 2Npartition (PART_nR×2N) and the partition index PartIdx is not 1 (NO instep S2102), (i.e., in case of 2N by 2N partition (PART_2N×2N), 2N by Npartition (PART_2N×N), 2N by nU partition (PART_2N×nU), 2N by nDpartition (PART_2N×nD), N by 2N partition (PART_N×2N), nL by 2Npartition (PART_nL×2N), or nR by 2N partition (PART_nR×2N), and thepartition index PartIdx is 0), coding information of a prediction blockA adjacent to the left of a prediction block subject to derivation isderived from the coding information storing memory 115 or 210 (stepS2111).

Subsequent processes of step S2113 through step S2115 are performed forL0 and L1 respectively (step S2112-S2116). In case of deriving areference index of L0 of a time merge candidate, LX is set to L0, and incase of deriving a reference index of L1, LX is set to L1. However, incase that the slice type slice_type is a P slice, an inter predictionmode only includes L0 prediction (Pred_L0) and does not include L1prediction (Pred_L1) nor bi-prediction (Pred_BI). Therefore a processregarding L1 can be omitted.

In case that a flag predFlagLX[xA][yA] indicating whether or not toperform LX prediction of a prediction block A is not 0 (YES in stepS2113), a reference index refIdxLXCol of LX of a time merge candidate isset to a value identical to the value of reference indexrefIdxLX[xA][yA] of LX of the prediction block A (step S2114). xA and yAare indexes indicating the position of an upper left pixel in aprediction block A in a picture.

According to the present embodiment, in prediction block N (N=A or B),in case that the prediction block N is outside a slice subject toencoding and decoded and cannot be used, in case that the predictionblock N has not been encoded because the prediction block N issubsequent to the prediction block subject to encoding or decoding inthe order of encoding or decoding so that the prediction block N cannotbe used, or in case that the prediction mode PredMode is intraprediction (MODE_INTRA), both flags, predFlagL0[xN][yN] indicatingwhether or not to use L0 prediction and predFlagL0[xN][yN] indicatingwhether or not to use L1 prediction, are 0. xN and yN are indexesindicating the position of an upper left pixel in a prediction block Nin a picture. In case that the prediction mode PredMode of theprediction block N is inter prediction (MODE_INTER) and the interprediction mode is L0 prediction (Pred_L0), the flag predFlagL0[xN][yN]indicating whether or not to use L0 prediction of the prediction block Nis 1, and the flag predFlagL0[xN][yN] indicating whether or not to useL1 prediction is 0. In case that the inter prediction mode of theprediction block N is L1 prediction (Pred_L1), the flagpredFlagL0[xN][yN] indicating whether or not to use L0 prediction of theprediction block N is 0, and the flag predFlagL0[xN][yN] indicatingwhether or not to use L1 prediction is 1. In case that the interprediction mode of the prediction block N is bi-prediction (Pred_BI),the flag predFlagL0[xN][yN] indicating whether or not to use L0prediction of the prediction block N and the flag predFlagL1[xN][yN]indicating whether or not to use L1 prediction are both 1.

In case that a flag predFlagLX[xA][yA] indicating whether or not toperform LX prediction of a prediction block A is 0 (NO in step S2113), areference index refIdxLXCol of LX of a time merge candidate is set to adefault value 0 (step S2115).

Processes of step S2113 through step S2115 are performed for L0 and L1respectively (step S2112-S2116), and the derivation process of areference index is completed.

On the other hand, in case that the partition mode (PartMode) is N by 2Npartition (PART_N×2N), nL by 2N partition (PART_nL×2N), or nR by 2Npartition (PART_nR×2N) and the partition index PartIdx is 1 (YES in stepS2102), coding information of a prediction B adjacent to the top of theprediction block subject to derivation is derived from the codinginformation storing memory 115 or 210 (step S2117).

Subsequent processes of step S2119 through step S2121 are performed forL0 and L1 respectively (step S2118-S2122). In case of deriving areference index of L0 of a time merge candidate, LX is set to L0, and incase of deriving a reference index of L1, LX is set to L1. However, incase that the slice type slice_type is a P slice, an inter predictionmode only includes L0 prediction (Pred_L0) and does not include L1prediction (Pred_L1) nor bi-prediction (Pred_BI). Therefore a processregarding L1 can be omitted.

In case that a flag predFlagLX[xB][yB] indicating whether or not toperform LX prediction of a prediction block B is not 0 (YES in stepS2119), a reference index refIdxLXCol of LX of a time merge candidate isset to a value identical to the value of reference indexrefIdxLX[xB][yB] of LX of the prediction block B (step S2120). xB and yBare indexes indicating the position of an upper left pixel in aprediction block B in a picture.

In case that a flag predFlagLX[xB][yB] indicating whether or not toperform LX prediction of a prediction block B is 0 (NO in step S2119), areference index refIdxLXCol of LX of a time merge candidate is set to adefault value 0 (step S2121).

Processes of step S2119 through step S2121 are performed for L0 and L1respectively (step S2118-S2122), and the derivation process of thereference index is completed.

Third Exemplary Embodiment

Next, an explanation will be given below on a third exemplary embodimentof the present embodiment. FIG. 24 shows adjacent blocks referred to inthe derivation process of a reference index of a time merge candidateaccording to the third exemplary embodiment of the present embodiment.According to the third exemplary embodiment of the present embodiment,in accordance with the partition mode (PartMode) of a prediction blockand the partition index PartIdx of the prediction block, which ofprediction blocks: a prediction block adjacent to the left edge of aprediction block subject to derivation; or a prediction block adjacentto the upper edge thereof is used is switched. In case of a predictionblock subject to derivation of which the partition index PartIdx is 0, aprediction block that is adjacent to a long edge, which has a highercorrelation, is referred to. In case of a prediction block subject toderivation of which the partition index PartIdx is 1, a prediction blockthat is adjacent to an edge outside the prediction block is referred to.In case that a partition mode (PartMode) is 2N by 2N partition(PART_2N×2N), as shown in FIG. 24A, a prediction block A0 adjacent tothe left of a prediction block subject to derivation is referred to, anda reference index of LX of a time merge candidate is set to a value ofreference index of LX of the prediction block A0.

In case that a partition mode (PartMode) is 2N by N partition(PART_2N×N), 2N by nU partition (PART_2N×nU), and 2N by nD partition(PART_2N×nD), where coding block subject to processing is partitionedinto two prediction blocks arranged vertically, as shown in FIGS. 24B,24C, and 24D, a prediction block BO adjacent to the upper edge, which isa long edge, is referred to for a prediction block subject to derivationof which the partition index PartIdx is 0, a reference index of LX oftime merge candidate is set to a value of reference index of LX ofprediction block B0. In case of a prediction block subject to derivationof which the partition index PartIdx is 1, a prediction block A1adjacent to the left edge, which is outside the coding block, isreferred to, and a reference index of LX of a time merge candidate isset to the value of reference index of LX of the prediction block A1.Since both prediction blocks B0 and A1 to refer to are outside of thecoding block, a reference index of time merge candidate of twoprediction blocks, of which the partition index PartIdx are 0 and 1respectively, can be derived in parallel, respectively.

In case that a partition mode (PartMode) is N by 2N partition(PART_N×2N), nL by 2N partition (PART_nL×2N), or nR by 2N partition(PART_nR×2N), where coding block subject to processing is partitionedinto two prediction blocks arranged horizontally, as shown in FIGS. 24E,24F, and 24G, a prediction block A0 adjacent to the left edge, which isa long edge, is referred to for a prediction block subject to derivationof which the partition index PartIdx is 0, a reference index of LX oftime merge candidate is set to a value of reference index of LX ofprediction block A0. In case of a prediction block subject to derivationof which the partition index PartIdx is 1, a prediction block B1adjacent to the upper edge, which is outside the coding block, isreferred to, and a reference index of LX of a time merge candidate isset to the value of reference index of LX of the prediction block B1.Since both prediction blocks A0 and B1 to refer to are outside of thecoding block, a reference index of time merge candidate of twoprediction blocks of which the partition index PartIdx are 0 and 1respectively, can be derived in parallel, respectively.

However, in case that prediction blocks A and B in the proximity do notperform LX prediction, a reference index of LX of a time merge candidateis set to a default value 0. The reason why the default value of areference index of LX of a time merge candidate is set to 0 in case thatprediction blocks A and B in the proximity do not perform LX predictionis that a reference picture corresponding to the reference index value 0has the highest possibility to be selected in inter prediction. However,the scope of the present invention is not limited to this example. Thedefault value of the reference index may be set to a value other than 0(e.g., 1, 2, etc.), or a syntax element indicating the default value ofthe reference index may be provided in a bitstream at a sequence level,at a picture level, or at a slice level, so that the syntax element canbe transmitted and selected at encoding.

FIG. 25 shows a flowchart illustrating procedure of derivation processof a reference index of a time merge candidate in step S202 of FIG. 18according to the third exemplary embodiment of the present embodiment.First, in case that the partition mode (PartMode) is 2N by N partition(PART_2N×N), 2N by nU partition (PART_2N×nU), 2N by nD partition(PART_2N×nD), and the partition index PartIdx is not 0, or in case thatthe partition mode is N by 2N partition (PART_N×2N), nL by 2N partition(PART_nL×2N), or nR by 2N partition (PART_nR×2N), and the partitionindex PartIdx is not 1 (NO in step S2103), in other words, in case thatthe partition mode is 2N by 2N partition (PART_2N×2N), in case that thepartition mode is 2N by N partition (PART_2N×N), 2N by nU partition(PART_2N×nU), or 2N by nD partition (PART_2N×nD), and the partitionindex PartIdx is 0, or in case that the partition mode is N by 2Npartition (PART_N×2N), nL by 2N partition (PART_nL×2N), or nR by 2Npartition (PART_nR×2N) and the partition index PartIdx is 0, codinginformation of a prediction block A adjacent to the left of a predictionblock subject to derivation is derived from the coding informationstoring memory 115 or 210 (step S2111).

Subsequent processes of step S2113 through step S2115 are performed forL0 and L1 respectively (step S2112-S2116). In case of deriving areference index of L0 of a time merge candidate, LX is set to L0, and incase of deriving a reference index of L1, LX is set to L1. However, incase that the slice type slice_type is a P slice, an inter predictionmode only includes L0 prediction (Pred_L0) and does not include L1prediction (Pred_L1) nor bi-prediction (Pred_BI). Therefore a processregarding L1 can be omitted.

In case that a flag predFlagLX[xA][yA] indicating whether or not toperform LX prediction of a prediction block A is not 0 (YES in stepS2113), a reference index refIdxLXCol of LX of a time merge candidate isset to a value identical to the value of reference indexrefIdxLX[xA][yA] of LX of the prediction block A (step S2114). xA and yAare indexes indicating the position of an upper left pixel in aprediction block A in a picture.

According to the present embodiment, in prediction block N (N=A or B),in case that the prediction block N is outside a slice subject toencoding and decoded and cannot be used, in case that the predictionblock N has not been encoded because the prediction block N issubsequent to the prediction block subject to encoding or decoding inthe order of encoding or decoding so that the prediction block N cannotbe used, or in case that the prediction mode PredMode is intraprediction (MODE_INTRA), both flags, predFlagL0[xN][yN] indicatingwhether or not to use L0 prediction and predFlagL1[xN][yN] indicatingwhether or not to use L1 prediction, are 0. xN and yN are indexesindicating the position of an upper left pixel in a prediction block Nin a picture. In case that the prediction mode PredMode of theprediction block N is inter prediction (MODE_INTER) and the interprediction mode is L0 prediction (Pred_L0), the flag predFlagL0[xN][yN]indicating whether or not to use L0 prediction of the prediction block Nis 1, and the flag predFlagL1[xN][yN] indicating whether or not to useL1 prediction is 0. In case that the inter prediction mode of theprediction block N is L1 prediction (Pred_L1), the flagpredFlagL0[xN][yN] indicating whether or not to use L0 prediction of theprediction block N is 0, and the flag predFlagL1[xN][yN] indicatingwhether or not to use L1 prediction is 1. In case that the interprediction mode of the prediction block N is bi-prediction (Pred_BI),the flag predFlagL0[xN][yN] indicating whether or not to use L0prediction of the prediction block N and the flag predFlagL1[xN][yN]indicating whether or not to use L1 prediction are both 1.

In case that a flag predFlagLX[xA][yA] indicating whether or not toperform LX prediction of a prediction block A is 0 (NO in step S2113), areference index refIdxLXCol of LX of a time merge candidate is set to adefault value 0 (step S2115).

Processes of step S2113 through step S2115 are performed for L0 and L1respectively (step S2112-S2116), and the derivation process of areference index is completed.

On the other hand, in case that the partition mode (PartMode) is N by 2Npartition (PART_N×2N), nL by 2N partition (PART_nL×2N), or nR by 2Npartition (PART_nR×2N) and the partition index PartIdx is 1 (YES in stepS2102), coding information of a prediction B adjacent to the top of theprediction block subject to derivation is derived from the codinginformation storing memory 115 or 210 (step S2117).

Subsequent processes of step S2119 through step S2121 are performed forL0 and L1 respectively (step S2118-S2122). In case of deriving areference index of L0 of a time merge candidate, LX is set to L0, and incase of deriving a reference index of L1, LX is set to L1. However, incase that the slice type slice_type is a P slice, an inter predictionmode only includes L0 prediction (Pred_L0) and does not include L1prediction (Pred_L1) nor bi-prediction (Pred_BI). Therefore a processregarding L1 can be omitted.

In case that a flag predFlagLX[xB][yB] indicating whether or not toperform LX prediction of a prediction block B is not 0 (YES in stepS2119), a reference index refIdxLXCol of LX of a time merge candidate isset to a value identical to the value of reference indexrefIdxLX[xB][yB] of LX of the prediction block B (step S2120). xB and yBare indexes indicating the position of an upper left pixel in aprediction block B in a picture.

In case that a flag predFlagLX[xB][yB] indicating whether or not toperform LX prediction of a prediction block B is 0 (NO in step S2119), areference index refIdxLXCol of LX of a time merge candidate is set to adefault value 0 (step S2121).

Processes of step S2119 through step S2121 are performed for L0 and L1respectively (step S2118-S2122), and the derivation process of thereference index is completed.

Fourth Exemplary Embodiment

Next, an explanation will be given below on a fourth exemplaryembodiment of the present embodiment. FIG. 26 shows adjacent blocksreferred to in the derivation process of a reference index of a timemerge candidate according to the fourth exemplary embodiment of thepresent embodiment. According to the fourth exemplary embodiment of thepresent embodiment, in accordance with the partition mode (PartMode) ofa coding block and the partition index PartIdx of the prediction block,whether or not to refer to a prediction block adjacent to the left edgeof a prediction block subject to derivation is switched. In case that aprediction block adjacent to the left edge is outside the coding block,the prediction block is referred to and in case that the predictionblock adjacent to the left edge is inside the coding block, theprediction block is not referred to and a default value is set. In casethat a partition mode (PartMode) is 2N by 2N partition (PART_2N×2N), asshown in FIG. 26A, a prediction block A0 adjacent to the left of aprediction block subject to derivation is referred to, and a referenceindex of LX of a time merge candidate is set to a value of referenceindex of LX of the prediction block A0.

In case that a partition mode (PartMode) is 2N by N partition(PART_2N×N), 2N by nU partition (PART_2N×nU), and 2N by nD partition(PART_2N×nD), where coding block subject to processing is partitionedinto two prediction blocks arranged vertically, as shown in FIGS. 26B,26C, and 26D, a prediction block A0 adjacent to the left is referred tofor a prediction block subject to derivation of which the partitionindex PartIdx is 0, and a reference index of LX of time merge candidateis set to a value of reference index of LX of prediction block A0. Incase of a prediction block subject to derivation of which the partitionindex PartIdx is 1, a prediction block A1 adjacent to the left isreferred to, and a reference index of LX of a time merge candidate isset to the value of reference index of LX of the prediction block A1.Since both prediction blocks A0 and A1 to refer to are outside of thecoding block, a reference index of time merge candidate of twoprediction blocks, of which the partition index PartIdx are 0 and 1respectively, can be derived in parallel, respectively.

In case that a partition mode (PartMode) is N by 2N partition(PART_N×2N), nL by 2N partition (PART_nL×2N), or nR by 2N partition(PART_nR×2N), where coding block subject to processing is partitionedinto two prediction blocks arranged horizontally, as shown in FIGS. 26E,26F, and 26G, a prediction block A0 adjacent to the left is referred tofor a prediction block subject to derivation of which the partitionindex PartIdx is 0, reference indexes of LX of time merge candidates areset to a value of reference index of LX of prediction block A0. In caseof a prediction block subject to derivation of which the partition indexPartIdx is 1, a prediction block in the proximity is not referred to,and a reference index of LX of a time merge candidate is set to adefault value 0. Since a prediction block A0 to be referred to isoutside of the coding block, a reference index of time merge candidateof two prediction blocks of which the partition index PartIdx are 0 and1 respectively, can be derived in parallel, respectively.

However, in case that a prediction blocks A does not perform LXprediction, a reference index of LX of a time merge candidate is set toa default value 0. The reason why the default value of a reference indexof LX of a time merge candidate is set to 0 in case that a predictionblock A in the proximity does not perform LX prediction or in case thata partition index PartIdx of a prediction block subject to derivation is1 is that a reference picture corresponding to the reference index value0 has the highest possibility to be selected in inter prediction.However, the scope of the present invention is not limited to thisexample. The default value of the reference index may be set to a valueother than 0 (e.g., 1, 2, etc.), or a syntax element indicating thedefault value of the reference index may be provided in a bitstream at asequence level, at a picture level, or at a slice level, so that thesyntax element can be transmitted and selected at encoding.

FIG. 27 shows a flowchart illustrating procedure of derivation processof a reference index of a time merge candidate in step S202 of FIG. 18according to the fourth exemplary embodiment of the present embodiment.First, in case that the partition mode (PartMode) is not N by 2Npartition (PART_N×2N), nL by 2N partition (PART_nL×2N), or nR by 2Npartition (PART_nR×2N) and the partition index PartIdx is not 1 (NO instep S2102), (i.e., in case of 2N by 2N partition (PART_2N×2N), 2N by Npartition (PART_2N×N), 2N by nU partition (PART_2N×nU), 2N by nDpartition (PART_2N×nD), N by 2N partition (PART_N×2N), nL by 2Npartition (PART_nL×2N), or nR by 2N partition (PART_nR×2N), and thepartition index PartIdx is 0), coding information of a prediction blockA adjacent to the left of a prediction block subject to derivation isderived from the coding information storing memory 115 or 210 (stepS2111).

Subsequent processes of step S2113 through step S2115 are performed forL0 and L1 respectively (step S2112-S2116). In case of deriving areference index of L0 of a time merge candidate, LX is set to L0, and incase of deriving a reference index of L1, LX is set to L1. However, incase that the slice type slice_type is a P slice, an inter predictionmode only includes L0 prediction (Pred_L0) and does not include L1prediction (Pred_L1) nor bi-prediction (Pred_BI). Therefore a processregarding L1 can be omitted.

In case that a flag predFlagLX[xA][yA] indicating whether or not toperform LX prediction of a prediction block A is not 0 (YES in stepS2113), a reference index refIdxLXCol of LX of a time merge candidate isset to a value identical to the value of reference indexrefIdxLX[xA][yA] of LX of the prediction block A (step S2114). xA and yAare indexes indicating the position of an upper left pixel in aprediction block A in a picture.

According to the present embodiment, in prediction block N (N=A or B),in case that the prediction block N is outside a slice subject toencoding and decoded and cannot be used, in case that the predictionblock N has not been encoded because the prediction block N issubsequent to the prediction block subject to encoding or decoding inthe order of encoding or decoding so that the prediction block N cannotbe used, or in case that the prediction mode PredMode is intraprediction (MODE_INTRA), both flags, predFlagL0[xN][yN] indicatingwhether or not to use L0 prediction and predFlagL0[xN][yN] indicatingwhether or not to use L1 prediction, are 0. xN and yN are indexesindicating the position of an upper left pixel in a prediction block Nin a picture. In case that the prediction mode PredMode of theprediction block N is inter prediction (MODE_INTER) and the interprediction mode is L0 prediction (Pred_L0), the flag predFlagL0[xN][yN]indicating whether or not to use L0 prediction of the prediction block Nis 1, and the flag predFlagL0[xN][yN] indicating whether or not to useL1 prediction is 0. In case that the inter prediction mode of theprediction block N is L1 prediction (Pred_L1), the flagpredFlagL0[xN][yN] indicating whether or not to use L0 prediction of theprediction block N is 0, and the flag predFlagL0[xN][yN] indicatingwhether or not to use L1 prediction is 1. In case that the interprediction mode of the prediction block N is bi-prediction (Pred_BI),the flag predFlagL0[xN][yN] indicating whether or not to use L0prediction of the prediction block N and the flag predFlagL0[xN][yN]indicating whether or not to use L1 prediction are both 1.

In case that a flag predFlagLX[xA][yA] indicating whether or not toperform LX prediction of a prediction block A is 0 (NO in step S2113), areference index refIdxLXCol of LX of a time merge candidate is set to adefault value 0 (step S2115).

Processes of step S2113 through step S2115 are performed for L0 and L1respectively (step S2112-S2116), and the derivation process of areference index is completed.

On the other hand, in case that the partition mode (PartMode) is N by 2Npartition (PART_N×2N), nL by 2N partition (PART_nL×2N), or nR by 2Npartition (PART_nR×2N) and the partition index PartIdx is 1 (YES in stepS2102), subsequent process of step S2121 is performed for each L0 and L1(step S2118-S2122). In case of deriving a reference index of L0 of atime merge candidate, LX is set to L0, and in case of deriving areference index of L1, LX is set to L1. However, in case that the slicetype slice_type is a P slice, an inter prediction mode only includes L0prediction (Pred_L0) and does not include L1 prediction (Pred_L1) norbi-prediction (Pred_BI). Therefore a process regarding L1 can beomitted.

A reference index refIdxLXCol of LX of a time merge candidate is set toa default value 0 (step S2121).

Processes up to S2121 are performed for L0 and L1 respectively (stepS2118-S2122), and the derivation process of the reference index iscompleted.

Fifth Exemplary Embodiment

Next, an explanation will be given below on a fifth exemplary embodimentof the present embodiment. FIG. 28 shows adjacent blocks referred to inthe derivation process of a reference index of a time merge candidateaccording to the fifth exemplary embodiment of the present embodiment.According to the fifth exemplary embodiment of the present embodiment,in accordance with the partition mode (PartMode), whether or not torefer to a prediction block adjacent to the left edge of a predictionblock subject to derivation is switched. A prediction block adjacent tothe edge outside of a coding block is referred to. In case that aprediction block adjacent to the left edge is outside the coding block,the prediction block is referred to and in case that the predictionblock adjacent to the left edge is inside the coding block, theprediction block is not referred to and a default value is set. In casethat a partition mode (PartMode) is 2N by 2N partition (PART_2N×2N), asshown in FIG. 28A, a prediction block A0 adjacent to the left of aprediction block subject to derivation is referred to, and a referenceindex of LX of a time merge candidate is set to a value of referenceindex of LX of the prediction block A0.

In case that a partition mode (PartMode) is 2N by N partition(PART_2N×N), 2N by nU partition (PART_2N×nU), and 2N by nD partition(PART_2N×nD), where coding block subject to processing is partitionedinto two prediction blocks arranged vertically, as shown in FIGS. 28B,28C, and 28D, a prediction block A0 adjacent to the left is referred tofor a prediction block subject to derivation of which the partitionindex PartIdx is 0, a reference index of LX of time merge candidate isset to a value of reference index of LX of prediction block A0. In caseof a prediction block subject to derivation of which the partition indexPartIdx is 1, a prediction block A1 adjacent to the left is referred to,and a reference index of LX of a time merge candidate is set to thevalue of reference index of LX of the prediction block A1. Since bothprediction blocks A0 and A1 to refer to are outside of the coding block,a reference index of time merge candidate of two prediction blocks, ofwhich the partition index PartIdx are 0 and 1 respectively, can bederived in parallel, respectively.

In case that a partition mode (PartMode) is N by 2N partition(PART_N×2N), nL by 2N partition (PART_nL×2N), or nR by 2N partition(PART_nR×2N), where coding block subject to processing is partitionedinto two prediction blocks arranged horizontally, in both cases of aprediction block of which the partition index PartIdx is 0 or 1, aprediction block in the proximity is not referred to, and a referenceindex of LX of a time merge candidate is set to a default value 0. Sincea prediction block in the proximity of a prediction block subject toprocessing is not referred to, a prediction block in the coding block isnot referred to, therefore a reference index of time merge candidate oftwo prediction blocks of which the partition index PartIdx are 0 and 1respectively, can be derived in parallel, respectively.

However, in case that a prediction blocks A does not perform LXprediction, a reference index of LX of a time merge candidate is set toa default value 0. The reason why the default value of a reference indexof LX of a time merge candidate is set to 0 in case that a predictionblock A in the proximity does not perform LX prediction or in case thatthe partition mode (PartMode) of a coding block including a predictionblock subject to derivation is N by 2N partition (PART_N×2N), nL by 2Npartition (PART_nL×2N), or nR by 2N partition is that a referencepicture corresponding to the reference index value 0 has the highestpossibility to be selected in inter prediction. However, the scope ofthe present invention is not limited to this example. The default valueof the reference index may be set to a value other than 0 (e.g., 1, 2,etc.), or a syntax element indicating the default value of the referenceindex may be provided in a bitstream at a sequence level, at a picturelevel, or at a slice level, so that the syntax element can betransmitted and selected at encoding.

FIG. 29 shows a flowchart illustrating procedure of derivation processof a reference index of a time merge candidate in step S202 of FIG. 18according to the fifth exemplary embodiment of the present embodiment.First, in case that the partition mode (PartMode) is not N by 2Npartition (PART_N×2N), nL by 2N partition (PART_nL×2N), or nR by 2Npartition (PART_nR×2N) (NO in step S2101), that is, in case of 2N by 2Npartition (PART_2N×2N), 2N by N partition (PART_2N×N), 2N by nUpartition (PART_2N×nU), 2N by nD partition (PART_2N×nD), codinginformation of a prediction block A adjacent to the left of a predictionblock subject to derivation is derived from the coding informationstoring memory 115 or 210 (step S2111).

Subsequent processes of step S2113 through step S2115 are performed forL0 and L1 respectively (step S2112-S2116). In case of deriving areference index of L0 of a time merge candidate, LX is set to L0, and incase of deriving a reference index of L1, LX is set to L1. However, incase that the slice type slice_type is a P slice, an inter predictionmode only includes L0 prediction (Pred_L0) and does not include L1prediction (Pred_L1) nor bi-prediction (Pred_BI). Therefore a processregarding L1 can be omitted.

In case that a flag predFlagLX[xA][yA] indicating whether or not toperform LX prediction of a prediction block A is not 0 (YES in stepS2113), a reference index refIdxLXCol of LX of a time merge candidate isset to a value identical to the value of reference indexrefIdxLX[xA][yA] of LX of the prediction block A (step S2114). xA and yAare indexes indicating the position of an upper left pixel in aprediction block A in a picture.

According to the present embodiment, in prediction block N (N=A or B),in case that the prediction block N is outside a slice subject toencoding and decoded and cannot be used, in case that the predictionblock N has not been encoded because the prediction block N issubsequent to the prediction block subject to encoding or decoding inthe order of encoding or decoding so that the prediction block N cannotbe used, or in case that the prediction mode PredMode is intraprediction (MODE_INTRA), both flags, predFlagL0[xN][yN] indicatingwhether or not to use L0 prediction and predFlagL1[xN][yN] indicatingwhether or not to use L1 prediction, are 0. xN and yN are indexesindicating the position of an upper left pixel in a prediction block Nin a picture. In case that the prediction mode PredMode of theprediction block N is inter prediction (MODE_INTER) and the interprediction mode is L0 prediction (Pred_L0), the flag predFlagL0[xN][yN]indicating whether or not to use L0 prediction of the prediction block Nis 1, and the flag predFlagL1[xN][yN] indicating whether or not to useL1 prediction is 0. In case that the inter prediction mode of theprediction block N is L1 prediction (Pred_L1), the flagpredFlagL0[xN][yN] indicating whether or not to use L0 prediction of theprediction block N is 0, and the flag predFlagL1[xN][yN] indicatingwhether or not to use L1 prediction is 1. In case that the interprediction mode of the prediction block N is bi-prediction (Pred_BI),the flag predFlagL0[xN][yN] indicating whether or not to use L0prediction of the prediction block N and the flag predFlagL1[xN][yN]indicating whether or not to use L1 prediction are both 1.

In case that a flag predFlagLX[xA][yA] indicating whether or not toperform LX prediction of a prediction block A is 0 (NO in step S2113), areference index refIdxLXCol of LX of a time merge candidate is set to adefault value 0 (step S2115).

Processes of step S2113 through step S2115 are performed for L0 and L1respectively (step S2112-S2116), and the derivation process of areference index is completed.

On the other hand, in case that the partition mode (PartMode) is N by 2Npartition (PART_N×2N), nL by 2N partition (PART_nL×2N), or nR by 2Npartition (PART_nR×2N) (YES in step S2101), subsequent process of stepS2121 is performed for each L0 and L1 (step S2118-S2122). In case ofderiving a reference index of L0 of a time merge candidate, LX is set toL0, and in case of deriving a reference index of L1, LX is set to L1.However, in case that the slice type slice_type is a P slice, an interprediction mode only includes L0 prediction (Pred_L0) and does notinclude L1 prediction (Pred_L1) nor bi-prediction (Pred_BI). Therefore aprocess regarding L1 can be omitted.

A reference index refIdxLXCol of LX of a time merge candidate is set toa default value 0 (step S2121).

Processes up to S2121 are performed for L0 and L1 respectively (stepS2118-S2122), and the derivation process of the reference index iscompleted.

Sixth Exemplary Embodiment

Next, an explanation will be given below on a sixth exemplary embodimentof the present embodiment. According to the sixth exemplary embodimentof the present embodiment, regardless of a partition mode (PartMode) ofa coding block including prediction mode subject to derivation (codingblock subject to processing), and a value of partition index PartIdx ofa prediction mode subject to derivation, prediction block in theproximity is not referred to, and a reference index of LX of a timemerge candidate is set to a default value 0. Since a prediction block inthe proximity of a prediction block subject to processing is notreferred to, a prediction block in the coding block is not referred to,therefore time merge candidates of two prediction blocks which isincluded in a same coding block and of which the partition index PartIdxare 0 and 1 respectively, can be derived in parallel, respectively.

The reason why the default value of a reference index of LX of a timemerge candidate is set to 0 is that a reference picture corresponding tothe reference index value 0 has the highest possibility to be selectedin inter prediction. However, the scope of the present invention is notlimited to this example. The default value of the reference index may beset to a value other than 0 (e.g., 1, 2, etc.), or a syntax elementindicating the default value of the reference index may be provided in abitstream at a sequence level, at a picture level, or at a slice level,so that the syntax element can be transmitted and selected at encoding.

In addition, according to the sixth exemplary embodiment, a referenceindex refIdxLXCol of LX of a time merge candidate is set to a defaultvalue 0 without referring to a block in the proximity. Therefore, thederivation process can be simplified in comparison with the first,second, third, fourth, fifth, and seventh (described later) embodiment.

FIG. 30 shows a flowchart illustrating procedure of derivation processof a reference index of a time merge candidate in step S202 of FIG. 18according to the sixth exemplary embodiment of the present embodiment.

A process of step S2115 is performed for L0 and L1 respectively (stepS2112-S2116). In case of deriving a reference index of L0 of a timemerge candidate, LX is set to L0, and in case of deriving a referenceindex of L1, LX is set to L1. However, in case that the slice typeslice_type is a P slice, an inter prediction mode only includes L0prediction (Pred_L0) and does not include L1 prediction (Pred_L1) norbi-prediction (Pred_BI). Therefore a process regarding L1 can beomitted.

A reference index refIdxLXCol of LX of a time merge candidate is set toa default value 0 (step S2115).

A process of step S2115 is performed for L0 and L1 respectively (stepS2112-S2116), and the derivation process of a reference index iscompleted.

Seventh Exemplary Embodiment

Next, an explanation will be given below on a seventh exemplaryembodiment of the present embodiment. FIG. 31 shows adjacent blocksreferred to in the derivation process of a reference index of a timemerge candidate according to the seventh exemplary embodiment of thepresent embodiment. According to the seventh exemplary embodiment of thepresent embodiment, regardless of a partition mode (PartMode) of acoding block including prediction mode subject to derivation (codingblock subject to processing), and a value of partition index PartIdx ofa prediction mode subject to derivation, prediction block A adjacent tothe left of a coding block subject to processing is referred to as shownin FIGS. 31A-31G, and a reference index of LX of a time merge candidateis set to a value of a reference index of LX of the prediction block A.Since a prediction block A to be referred to is outside of the codingblock, a reference index of time merge candidate of two predictionblocks of which the partition index PartIdx are 0 and 1 respectively,can be derived in parallel, respectively.

However, in case that a prediction blocks A does not perform LXprediction, a reference index of LX of a time merge candidate is set toa default value 0. The reason why the default value of a reference indexof LX of a time merge candidate is set to 0 in case that the predictionblock A in the proximity does not perform LX prediction is that areference picture corresponding to the reference index value 0 has thehighest possibility to be selected in inter prediction. However, thescope of the present invention is not limited to this example. Thedefault value of the reference index may be set to a value other than 0(e.g., 1, 2, etc.), or a syntax element indicating the default value ofthe reference index may be provided in a bitstream at a sequence level,at a picture level, or at a slice level, so that the syntax element canbe transmitted and selected at encoding.

According to the sixth exemplary embodiment, reference indexes of timemerge candidates of respective prediction blocks in the coding block areset to a common value. Therefore, it is not required to derive areference index of time merge candidate for each prediction block, sothat the derivation process can be simplified.

FIG. 32 shows a flowchart illustrating procedure of derivation processof a reference index of a time merge candidate in step S202 of FIG. 18according to the seventh exemplary embodiment of the present embodiment.First, coding information on a prediction block A adjacent to the leftof a coding block subject to processing is derived from the codinginformation storing memory 115 or 210 (step S2131).

Subsequent processes of step S2133 through step S2135 are performed forL0 and L1 respectively (step S2132-S2136). In case of deriving areference index of L0 of a time merge candidate, LX is set to L0, and incase of deriving a reference index of L1, LX is set to L1. However, incase that the slice type slice_type is a P slice, an inter predictionmode only includes L0 prediction (Pred_L0) and does not include L1prediction (Pred_L1) nor bi-prediction (Pred_BI). Therefore a processregarding L1 can be omitted.

In case that a flag predFlagLX[xA][yA] indicating whether or not toperform LX prediction of a prediction block A, which is adjacent to theleft of a coding block subject to processing, is not 0 (YES in stepS2133), a reference index refIdxLXCol of LX of a time merge candidate isset to a value identical to the value of reference indexrefIdxLX[xA][yA] of LX of the prediction block A (step S2134). xA and yAare indexes indicating the position of an upper left pixel in aprediction block A, which is adjacent to the left of a coding blocksubject to processing, in a picture.

According to the present embodiment, in prediction block N (N=A or B),in case that the prediction block N is outside a slice subject toencoding and decoded and cannot be used, in case that the predictionblock N has not been encoded because the prediction block N issubsequent to the prediction block subject to encoding or decoding inthe order of encoding or decoding so that the prediction block N cannotbe used, or in case that the prediction mode PredMode is intraprediction (MODE_INTRA), both flags, predFlagL0[xN][yN] indicatingwhether or not to use L0 prediction and predFlagL1[xN][yN] indicatingwhether or not to use L1 prediction, are 0. xN and yN are indexesindicating the position of an upper left pixel in a prediction block Nin a picture. In case that the prediction mode PredMode of theprediction block N is inter prediction (MODE_INTER) and the interprediction mode is L0 prediction (Pred_L0), the flag predFlagL0[xN][yN]indicating whether or not to use L0 prediction of the prediction block Nis 1, and the flag predFlagL1[xN][yN] indicating whether or not to useL1 prediction is 0. In case that the inter prediction mode of theprediction block N is L1 prediction (Pred_L1), the flagpredFlagL0[xN][yN] indicating whether or not to use L0 prediction of theprediction block N is 0, and the flag predFlagL1[xN][yN] indicatingwhether or not to use L1 prediction is 1. In case that the interprediction mode of the prediction block N is bi-prediction (Pred_BI),the flag predFlagL0[xN][yN] indicating whether or not to use L0prediction of the prediction block N and the flag predFlagL1[xN][yN]indicating whether or not to use L1 prediction are both 1.

In case that a flag predFlagLX[xA][yA] indicating whether or not toperform LX prediction of a prediction block A is 0 (NO in step S2133), areference index refIdxLXCol of LX of a time merge candidate is set to adefault value 0 (step S2135).

Processes of step S2133 through step S2135 are performed for L0 and L1respectively (step S2132-S2136), and the derivation process of areference index is completed.

Although whether or not to refer to a prediction block adjacent to theleft edge of a coding block including a prediction block subject toderivation is switched according to the seventh exemplary embodiment,instead of the prediction block adjacent to the left edge, whether ornot to refer to a prediction block adjacent to the upper edge may beswitched.

Eighth Exemplary Embodiment

Next, an explanation will be given below on an eighth exemplaryembodiment of the present embodiment. FIG. 43 shows adjacent blocksreferred to in the derivation process of a reference index of a timemerge candidate according to the eighth exemplary embodiment of thepresent embodiment. According to the eighth exemplary embodiment of thepresent embodiment, regardless of the partition mode (PartMode) of acoding block, and in accordance with the partition index PartIdx of aprediction block, whether or not to refer to a prediction block adjacentto the left edge of a prediction block subject to derivation isswitched. In case that the partition index PartIdx of a prediction blockis 0, a prediction block adjacent to the left edge is referred to, andin case that the partition index PartIdx is a value other than 0, aprediction block in the proximity is not referred to, and a defaultvalue is set. In case that the partition index PartIdx of a predictionblock is 0, a prediction block adjacent to the left edge is alwaysoutside the coding block in any partition mode (PartMode). However, incase that the partition index PartIdx is a value other than 0, aprediction block adjacent to the left edge may be inside the codingblock depending on the partition mode (PartMode). As shown in FIG. 43A,a prediction block A0 adjacent to the left of a prediction block subjectto derivation is referred to, and a reference index of LX of a timemerge candidate is set to a value of reference index of LX of theprediction block A0.

In case that a partition mode (PartMode) is 2N by N partition(PART_2N×N), 2N by nU partition (PART_2N×nU), and 2N by nD partition(PART_2N×nD), where coding block subject to processing is partitionedinto two prediction blocks arranged vertically, or in case that apartition mode (PartMode) is N by 2N partition (PART_N×2N), nL by 2Npartition (PART_nL×2N), or nR by 2N partition (PART_nR×2N), as shown inFIGS. 43B, 43C, 43D, 43E, 43F, and 43G, a prediction block A0 adjacentto the left is referred to for a prediction block subject to derivationof which the partition index PartIdx is 0, and a reference index of LXof time merge candidate is set to a value of reference index of LX ofprediction block A0. In case of a prediction block subject to derivationof which the partition index PartIdx is 1, a prediction block in theproximity is not referred to, and a reference index of LX of a timemerge candidate is set to a default value 0. Since a prediction block A0to be referred to is outside of the coding block, a reference index oftime merge candidate of two prediction blocks of which the partitionindex PartIdx are 0 and 1 respectively, can be derived in parallel,respectively.

However, in case that a prediction blocks A does not perform LXprediction, a reference index of LX of a time merge candidate is set toa default value 0. The reason why the default value of a reference indexof LX of a time merge candidate is set to 0 in case that a predictionblock A in the proximity does not perform LX prediction or in case thata partition index PartIdx of a prediction block subject to derivation is1 is that a reference picture corresponding to the reference index value0 has the highest possibility to be selected in inter prediction.However, the scope of the present invention is not limited to thisexample. The default value of the reference index may be set to a valueother than 0 (e.g., 1, 2, etc.), or a syntax element indicating thedefault value of the reference index may be provided in a bitstream at asequence level, at a picture level, or at a slice level, so that thesyntax element can be transmitted and selected at encoding.

FIG. 44 shows a flowchart illustrating procedure of derivation processof a reference index of a time merge candidate in step S202 of FIG. 18according to the eighth exemplary embodiment of the present embodiment.First, in case that the partition index PartIdx is 0 (YES in stepS2104), coding information on a prediction block A adjacent to the leftof a prediction block subject to derivation is derived from the codinginformation storing memory 115 or 210 (step S2111).

Subsequent processes of step S2113 through step S2115 are performed forL0 and L1 respectively (step S2112-S2116). In case of deriving areference index of L0 of a time merge candidate, LX is set to L0, and incase of deriving a reference index of L1, LX is set to L1. However, incase that the slice type slice_type is a P slice, an inter predictionmode only includes L0 prediction (Pred_L0) and does not include L1prediction (Pred_L1) nor bi-prediction (Pred_BI). Therefore a processregarding L1 can be omitted.

In case that a flag predFlagLX[xA][yA] indicating whether or not toperform LX prediction of a prediction block A is not 0 (YES in stepS2113), a reference index refIdxLXCol of LX of a time merge candidate isset to a value identical to the value of reference indexrefIdxLX[xA][yA] of LX of the prediction block A (step S2114). xA and yAare indexes indicating the position of an upper left pixel in aprediction block A in a picture.

According to the present embodiment, in prediction block N (N=A or B),in case that the prediction block N is outside a slice subject toencoding and decoded and cannot be used, in case that the predictionblock N has not been encoded because the prediction block N issubsequent to the prediction block subject to encoding or decoding inthe order of encoding or decoding so that the prediction block N cannotbe used, or in case that the prediction mode PredMode is intraprediction (MODE_INTRA), both flags, predFlagL0[xN][yN] indicatingwhether or not to use L0 prediction and predFlagL1[xN][yN] indicatingwhether or not to use L1 prediction, are 0. xN and yN are indexesindicating the position of an upper left pixel in a prediction block Nin a picture. In case that the prediction mode PredMode of theprediction block N is inter prediction (MODE_INTER) and the interprediction mode is L0 prediction (Pred_L0), the flag predFlagL0[xN][yN]indicating whether or not to use L0 prediction of the prediction block Nis 1, and the flag predFlagL1[xN][yN] indicating whether or not to useL1 prediction is 0. In case that the inter prediction mode of theprediction block N is L1 prediction (Pred_L1), the flagpredFlagL0[xN][yN] indicating whether or not to use L0 prediction of theprediction block N is 0, and the flag predFlagL1[xN][yN] indicatingwhether or not to use L1 prediction is 1. In case that the interprediction mode of the prediction block N is bi-prediction (Pred_BI),the flag predFlagL0[xN][yN] indicating whether or not to use L0prediction of the prediction block N and the flag predFlagL1[xN][yN]indicating whether or not to use L1 prediction are both 1.

In case that a flag predFlagLX[xA][yA] indicating whether or not toperform LX prediction of a prediction block A is 0 (NO in step S2113), areference index refIdxLXCol of LX of a time merge candidate is set to adefault value 0 (step S2115).

Processes of step S2113 through step S2115 are performed for L0 and L1respectively (step S2112-S2116), and the derivation process of areference index is completed.

On the other hand, in case that the partition index PartIdx is not 0 (NOin step S2104), subsequent process of step S2121 is performed for eachL0 and L1 (step S2118-S2122). In case of deriving a reference index ofL0 of a time merge candidate, LX is set to L0, and in case of deriving areference index of L1, LX is set to L1. However, in case that the slicetype slice_type is a P slice, an inter prediction mode only includes L0prediction (Pred_L0) and does not include L1 prediction (Pred_L1) norbi-prediction (Pred_BI). Therefore a process regarding L1 can beomitted.

A reference index refIdxLXCol of LX of a time merge candidate is set toa default value 0 (step S2121).

Processes up to S2121 are performed for L0 and L1 respectively (stepS2118-S2122), and the derivation process of the reference index iscompleted.

Although whether or not to refer to a prediction block adjacent to theleft edge of a prediction block subject to derivation is switchedaccording to the eighth exemplary embodiment, instead of the predictionblock adjacent to the left edge, whether or not to refer to a predictionblock adjacent to the upper edge may be switched.

Although it is assumed that N by N partition (PART_N×N) is not definedas a partition mode (PartMode) of a coding block according to thepresent embodiment, it is also possible to define the N by N partition(PART_N×N). Also in case that a partition mode (PartMode) is N by Npartition (PART_N×N), when deriving a reference index of a time mergecandidate of a prediction block included in a coding block subject toprocessing, by deriving the reference index without referring to aprediction block in the proximity, which is included in a coding blockidentical to a coding block included in a prediction block subject toprocessing, reference indexes of time merge candidates of fourprediction blocks, of which the partition index PartIdx are 0, 1, 2, and3 respectively, can be derived in parallel, respectively.

For example, in case of N by N partition (PART_N×N), a prediction blockin the proximity is not referred to, and a reference index of LX of atime merge candidate is set to a default value 0. Since a predictionblock in the proximity of a prediction block subject to derivation isnot referred to, reference indexes of time merge candidates of fourprediction blocks of which the partition index PartIdx are 0, 1, 2, and3 respectively, can be derived in parallel, respectively.

Alternatively, a reference index of a block in the proximity can bereferred to so that a reference index of a time merge candidate can bederived. FIG. 33 illustrates adjacent blocks referred to in thederivation process of a reference index of a time merge candidate of acoding block of N by N partition (PART_N×N).

As shown in FIG. 33A, in case of a prediction block subject toderivation of which the partition index PartIdx is 0, a prediction blockA0 adjacent to the left is referred to, and a reference index of LX of atime merge candidate is set to a value of reference index of LX of theprediction block A0. In case of a prediction block subject to derivationof which the partition index PartIdx is 1, a prediction block B1adjacent to the top is referred to, and a reference index of LX of atime merge candidate is set to the value of the reference index of LX ofthe prediction block B1. In case of a prediction block subject toderivation of which the partition index PartIdx is 2, a prediction blockA2 adjacent to the left is referred to, and a reference index of LX of atime merge candidate is set to a value of reference index of LX of theprediction block A2. In case of a prediction block subject to derivationof which the partition index PartIdx is 3, a prediction block in theproximity is not referred to, and a reference index of LX of a timemerge candidate is set to a default value 0. Since prediction blocks A0and A2, adjacent to the left of a prediction block subject toprocessing, and B1, adjacent to the top thereof, are all outside of thecoding block, reference indexes of time merge candidates of fourprediction blocks of which the partition index PartIdx are 0, 1, 2, and3 respectively, can be derived in parallel, respectively.

Alternatively, as shown in FIG. 33B, in case of a prediction blocksubject to derivation of which the partition index PartIdx is 0, aprediction block A0 adjacent to the left is referred to, and a referenceindex of LX of a time merge candidate is set to a value of the referenceindex of LX of the prediction block A0. In case of a prediction blocksubject to derivation of which the partition index PartIdx is 2, aprediction block A2 adjacent to the left is referred to, and a referenceindex of LX of a time merge candidate is set to a value of referenceindex of LX of the prediction block A2. In case of a prediction blocksubject to derivation of which the partition index PartIdx is 1 or 3, aprediction block in the proximity is not referred to, and a referenceindex of LX of a time merge candidate is set to a default value 0. Sinceboth prediction blocks A0 and A2 adjacent to the left of a predictionblock subject to processing are outside of the coding block, referenceindexes of time merge candidates of four prediction blocks of which thepartition index PartIdx are 0, 1, 2, and 3 can be derived respectivelyin parallel.

Alternatively, as shown in FIG. 33C, a prediction block A adjacent tothe left of a coding block subject to processing is referred to, and areference index of LX of a time merge candidate is set to a value ofreference index of LX of the prediction block A. Since a predictionblock A adjacent to the left of a coding block subject to processing isoutside of the coding block, reference indexes of time merge candidatesof four prediction blocks of which the partition index PartIdx are 0, 1,2, and 3 can be derived respectively in parallel.

Alternatively, as shown in FIG. 33D, in case of a prediction blocksubject to derivation of which the partition index PartIdx is 0, aprediction block A0 adjacent to the left is referred to, and a referenceindex of LX of a time merge candidate is set to a value of the referenceindex of LX of the prediction block A0. In case of a prediction blocksubject to derivation of which the partition index PartIdx is other than0 (PartIdx is 1, 2, or 3), a prediction block in the proximity is notreferred to, and a reference index of LX of a time merge candidate isset to a default value 0. Since a prediction block A0 adjacent to theleft of a prediction block subject to processing is outside of thecoding block, reference indexes of time merge candidates of fourprediction blocks of which the partition index PartIdx are 0, 1, 2, and3 can be derived respectively in parallel.

Next, a detailed explanation will be given on a method for deriving amerge candidate by using inter prediction information on a picture of adifferent time of step S203 of FIG. 18. FIG. 34 shows a flowchartillustrating procedure of time merge candidate derivation process ofstep S203 in FIG. 18.

First, a picture colPic of a different time is derived by a slice typeslice_type and a flag collocated_from_l0_flag described above (stepS3101).

FIG. 35 shows a flowchart illustrating procedure of derivation processof a picture colPic of a different time of step S3101 in FIG. 34. Incase that a slice type slice_type is a B slice and a flagcollocated_from_l0_flag described above is 0 (YES in step S3201 and YESin step S3202), RefPicList1[0] (i.e., a picture of which the referenceindex of reference list L1 is 0) is defined as a picture colPic of adifferent time (step S3203). Otherwise, that is, in case that a slicetype slice_type is a B slice and a flag collocated_from_l0_flagdescribed above is 1 (YES in step S3201 and NO in step S3202), or incase that a slice type slice_type is a P slice (NO in step S3201 and YESin step S3204), RefPicList0[0] (i.e., a picture of which the referenceindex of reference list L0 is 0) is defined as a picture colPic of adifferent time (step S3205).

Next, referring back to the flow chart of FIG. 34, a prediction blockcolPU of a different time is derived, and coding information is derived(step S3102).

FIG. 36 shows a flowchart illustrating procedure of derivation processof a prediction block colPU of a picture colPic of a different time ofstep S3102 in FIG. 34.

First, in a picture colPic of a different time, a prediction blockpositioned at a lower right (outside) of a position identical to aprediction block subject to processing is used as a prediction blockcolPU of a different time (step S3301). This prediction blockcorresponds to the prediction block T0 in FIG. 9.

Next, coding information of the prediction block colPU of a differenttime is derived (step S3302). In case that PredMode of the predictionblock colPU of a different time cannot be used or in case that theprediction mode PredMode of the prediction block colPU of a differenttime is intra prediction (MODE_INTRA) (YES in step S3303), and YES instep S3304), in a picture colPic of a different time, a prediction blockat an upper left in the middle of a position identical to a predictionblock subject to processing is used as a prediction block colPU of adifferent time (step S3305). This prediction block corresponds to theprediction block T1 in FIG. 9.

Next, referring back to the flow chart of FIG. 34, a motion vectorpredictor mvL1Col of L0 that is derived from a prediction block inanother picture at a position identical to a prediction block subject toencoding or decoding, and a flag availableFlagL0Col indicating whetheror not a time merge candidate Col is valid are derived (step S3103), anda motion vector predictor mvL1Col of L1 and a flag availableFlagColindicating whether or not the time merge candidate Col is valid arederived. In addition, in case that the flag availableFlagL0Col or theflag availableFlagL0Col is 1, the flag availableFlagCol indicatingwhether or not the time merge candidate Col is valid is set to 1.

FIG. 37 shows a flowchart illustrating procedure of derivation processof inter prediction information of time merge candidate of step S3103and step 3104 in FIG. 34. For L0 or L1, a list of target to derive timemerge candidate is defined as LX, and prediction using LX is referred toas LX prediction, unless otherwise noted. In case of being called asstep S3103, which is a derivation process of L0 of time merge candidate,LX is set to L0, and in case of being called as step S3104, which is aderivation process of L1 of time merge candidate, LX is set to L1.

In case that a prediction mode PredMode of a prediction block colPU of adifferent time is intra prediction (MODE_INTRA) or cannot be used, (NOin step S3401, NO in step S3402), a flag availableFlagLXCol and a flagpredFlagLXCol are both set to 0 (step S3403), a motion vector mvLXCol isset to (0,0) (step S3404), the derivation process of inter predictioninformation of time merge candidate is completed.

In case that a prediction block colPU is available and in case that aprediction mode PredMode is not intra prediction (MODE_INTRA) (YES instep S3401, YES in step S3402), mvCol, refIdxCol, and availableFlagColare derived in the following procedure.

In case that a flag PredFlagL0[xPCol][yPCol], which indicates whether ornot the L0 prediction of the prediction block colPU, is 0 (YES in stepS3405), the prediction mode of the prediction block colPU is Pred_L1.Therefore, a motion vector mvCol is set to a value identical to that ofMvL1[xPCol][yPCol], which is a motion vector of L1 of the predictionblock colPU (step S3406), and a reference index refIdxCol is set to avalue identical to that of a reference index RefIdxL1[xPCol][yPCol] ofL1 (step S3407), and a list ListCol is set to L1 (step S3408). xPCol andyPCol are indexes indicating the position of an upper left pixel of aprediction block colPU in a picture colPic of a different time.

On the other hand, in case that the L0 prediction flagPredFlagL0[xPCol][yPCol] of the prediction block colPU is not 0 (NO instep S3405 in FIG. 37), whether or not the L1 prediction flagPredFlagL1[xPCol][yPCol] of the prediction block colPU is 0 isdetermined. In case that the L1 prediction flag PredFlagL1[xPCol][yPCol]of the prediction block colPU is 0 (YES in step S3409), a motion vectormvCol is set to a value identical to that of MvL0[xPCol][yPCol], whichis a motion vector of L0 of the prediction block colPU (step S3410), anda reference index refIdxCol is set to a value identical to that of areference index RefIdxL0[xPCol][yPCol] of L0 (step S3411), and a listListCol is set to L0 (step S3412).

On the other hand, in case that both L0 prediction flagPredFlagL0[xPCol][yPCol] of prediction block colPU and L1 predictionflag PredFlagL1[xPCol][yPCol] of prediction block colPU are not 0 (NO instep S3405 and NO in step S3409), the inter prediction mode of theprediction block colPU is bi-prediction (Pred_BI). Therefore, one of twomotion vectors L0 and L1 is selected (step S3413).

FIG. 38 shows a flowchart indicating procedure of derivation process ofinter prediction information of time merge candidate when the interprediction mode of the prediction block colPU is bi-prediction(Pred_BI).

First, whether or not POCs of all pictures registered in all referencelists are smaller than POC of a picture subject to encoding or decodingcurrently is determined (step S3501). In case that POCs of all picturesregistered in L0 or L1, L0 and L1 being all reference lists ofprediction block colPU, are smaller than POC of a picture subject toencoding or decoding currently (YES in step S3501) and LX is L0, thatis, a prediction vector candidate of a motion vector of L0 of a picturesubject to encoding or decode is derived (YES in step S3502), interprediction information of L0 of the prediction block colPU is selected,and in case that LX is L1, that is, a prediction vector candidate of amotion vector of L1 of a picture subject to encoding or decode isderived (NO in step S3502), inter prediction information of L1 of theprediction block colPU is selected. On the other hand, in case that atleast one of the POC of pictures registered in any of all referencelists L0 and L1 of prediction block colPU is bigger than the POC of apicture subject to encoding or decoding currently (NO in step S3501) andflag collocated_from_l0_flag is 0 (YES in step S3503), inter predictioninformation of L0 of the prediction block colPU is selected, and in casethat flag collocated_from_l0_flag is 1 (NO in step S3503), interprediction information of L1 of the prediction block colPU is selected.

In case of selecting inter prediction information of L0 of theprediction block colPU (YES in step and YES in step S3503), a motionvector mvCol is set to a value identical to that of MvL0[xPCol][yPCol](step S3504), and a reference index refIdxCol is set to a valueidentical to that of RefIdxL0[xPCol][yPCol] (step S3505), and a listListCol is set to L0 (step S3506).

In case of selecting inter prediction information of L1 of theprediction block colPU (NO in step S2502 and NO in step S3503), a motionvector mvCol is set to a value identical to that of MvL1[xPCol][yPCol](step S3507), and a reference index refIdxCol is set to a valueidentical to that of RefIdxL1[xPCol][yPCol] (step S3508), and a listListCol is set to L1 (step S3509).

Referring back to FIG. 37, if inter prediction information can bederived from a prediction block colPU, a flag availableFlagLXCol and aflag predFlagLXCol are both set to 1 (step S3414).

Subsequently, a motion vector mvCol is scaled and defined as a motionvector mvLXCol of LX of a time merge candidate (step S3415). Anexplanation will be given on procedure of scaling computation process ofthe motion vector, while referring to FIGS. 39 and 40.

FIG. 39 shows a flowchart indicating procedure of scaling computationprocess of the motion vector of step S3105 in FIG. 34.

By subtracting POC of a reference picture corresponding to a referenceindex refIdxCol referred to in a list ListCol of a prediction blockcolPU from POC of picture colPic of a different time, a distance tdbetween pictures is derived (step S3601). In case that POC of areference picture referred to in a list ListCol of a prediction blockcolPU is previous to the picture colPic of a different time in thedisplay order, the distance td between pictures is a positive value, andin case that POC of a reference picture referred to in a list ListCol ofa prediction block colPU is subsequent to the picture colPic of adifferent time in the display order, the distance td between pictures isa negative value.

td=POC of prediction block colPU of a different time−POC of a referencepicture referred to in a list ListCol of a prediction block colPU.

By subtracting POC of a reference picture corresponding to a referenceindex of LX of a time merge candidate derived in step S202 in FIG. 18from POC of a picture subject to encoding or decoding currently, adistance tb between pictures is derived (step S3602). In case that thereference picture referred to in a list LX of a picture subject toencoding or decoding currently is previous to the picture subject toencoding or decoding currently in the display order, the distance tbbetween pictures is a positive value, and in case the reference picturereferred to in a list LX of a picture subject to encoding or decodingcurrently is subsequent to the other in the display order, the distancetb between pictures is a negative value. tb=POC of picture subject toencoding or decoding currently—POC of a reference picture correspondingto a reference index of LX of a time merge candidate

Subsequently, distances td between pictures and tb between pictures arecompared (step S3603). In case that the distances td and tb areidentical to each other (YES in step S3603), the motion vector mvLXColof LX of time merge candidate is set to a value identical to that of themotion vector mvCol (step S3604), the scaling computation process iscompleted.

mvLXCol=mvCol

On the other hand, in case that the distances td and tb are notidentical (NO in step S3603), scaling computation process is performedby multiplying mvCol by tb or td in accordance with the followingequation (step S3605), and a scaled motion vector mvLXCol of LX of timemerge candidate is obtained.

mvLXCol=tb or td*mvCol

FIG. 4 indicates an example in case that the scaling computation of stepS3605 is performed with precision of integer. Processes of stepS3606-step S3608 in FIG. 40 correspond to the step S3605 of FIG. 40.

First, in a similar manner to that of the flowchart shown in FIG. 39, adistance td between pictures and a distance tb between pictures arederived (step S3601 and step S3602).

Subsequently, distances td between pictures and tb between pictures arecompared (step S3603). In case that the distances td and tb areidentical (YES in step S3603), the motion vector mvLXCol of LX of timemerge candidate is set to a value identical to that of the motion vectormvCol (step S3604) in a similar manner to the flow chart in FIG. 39, thescaling computation process is completed.

mvLXCol=mvCol

On the other hand, in case that the distances td and tb are notidentical (NO in step S3603) a parameter tx is derived in accordancewith the following equation (step S3606).

tx=(16384+Abs(td or 2)) or td

Next, a scaling factor DistScaleFactor is derived in accordance with thefollowing equation (step S3607).

DistScaleFactor=(tb*tx+32)>>6

Subsequently, a scaled motion vector mvLXCol of LX of time mergecandidate is obtained in accordance with the following equation (stepS3608).

mvLXCol=ClipMv(Sign(DistScaleFactor*mvCol)*((Abs(DistScaleFactor*mvCol)+127)>>8))

Next, a detailed explanation will be given on a method of step S204 inFIG. 18 for registering a merge candidate in a merge candidate list andconstructing a merge candidate list. FIG. 41 shows a flowchartindicating a processing procedure for constructing a merge candidatelist. According to the method, by setting priorities and registering amerge candidate from the higher priority in a merge candid listmergeCandList, the amount of code of merge index merge_idx[x0][y0] isreduced. By putting an element of higher priority in the upper part ofthe merge candidate list, the amount of code is reduced. For example, incase that there are five elements in the merge candidate listmergeCandList, an index 0 of the merge candidate list is set to “0”, anindex 1 thereof is set to “10”, an index 2 thereof is set to “110”, anindex 3 thereof is set to “1110”, and an index 4 thereof is set to“11110”, by which, the amount of code representing the index 0 becomes 1bit. By registering elements that is considered to occur in highfrequency in index 1, the amount of code is reduced.

The merge candidate list mergeCandList is configured as a liststructure, and in which a merge index indicating locations in the mergecandidate list, and a storage area that stores a merge candidatecorresponding to the index as an element are provided. The number ofmerge index starts from 0, and a merge candidate is stored in a storagearea of the merge candidate list mergeCandList. In the followingprocess, a prediction block that becomes a merge candidate of amergeindex i registered in the merge candidate list mergeCandList isreferred to as mergeCandList[i], which is distinguished from the mergecandidate list mergeCandList by array notation.

First, in case that availableFlagA is 1 (YES in step S4101), a mergecandidate A is registered at the top of the merge candidate listmergeCandList (step S4102).

Subsequently, in case that availableFlagB is 1 (YES in step S4103), amerge candidate B is registered at the end of the merge candidate listmergeCandList (step S4104).Subsequently, in case that availableFlagC is 1 (YES in step S4105), amerge candidate C is registered at the end of the merge candidate listmergeCandList (step S4106).Subsequently, in case that availableFlagD is 1 (YES in step S4107), amerge candidate D is registered at the end of the merge candidate listmergeCandList (step S4108).Subsequently, in case that availableFlagE is 1 (YES in step S4109), amerge candidate E is registered at the end of the merge candidate listmergeCandList (step S4110).Subsequently, in case that vailableFlagCol is 1 (YES in step S4109), amerge candidate Col is registered at the end of the merge candidate listmergeCandList (step S4110).

In a merge mode, a prediction block A adjacent to the left and aprediction block B adjacent to the top often with the prediction blocksubject to encoding or decoding in an integrated manner. In case thatthe inter prediction information of prediction blocks A and B can bederived, the merge candidates A and B are registered ahead of othermerge candidates C, D, E, and Col in the candidate list, preferentially.

In FIG. 13, in the coding information selection unit 136 of the interprediction information derivation unit 104 of the moving pictureencoding device, a merge candidate is selected from merge candidatesregistered in the merge candidate list, and a merge index and interprediction information of a merge candidate corresponding to the mergeindex is provided to the motion compensation prediction unit 105.

When selecting a merge candidate, a method similar to that of theprediction method determining unit 107 can be used. Coding informationand coding distortion between an amount of code of coding informationand a residual signal, and coding distortion between a predictionpicture signal and a picture signal are derived for each mergecandidate. A merge candidate that has the least amount of generated codeand coding distortion is determined. For each merge candidate, entropyencoding is performed of syntax element merge_idx, which is codinginformation of a merge mode, is performed, and an amount of code ofcoding information is calculated. Further, for each merge candidate, anamount of code of an encoded prediction residual signal is calculatedwith a method similar to that of the motion compensation prediction unit105. The prediction residual signal is a residual signal between aprediction picture signal, on which motion compensation is performed inaccordance with inter prediction information of each merge candidate,and a picture signal, which is subject to encoding and which is providedfrom the picture memory 101. Total amount of code, to which an amount ofcode of coding information (i.e., a merge index) and an amount of codeof prediction residual signal is added is calculated and set as anevaluation value.

After encoding such prediction residual signal, decoding for evaluatingan amount of distortion is performed, and a coding distortion iscalculated as a ratio representing an error from an original picturesignal, the error arising from encoding. By comparing the total amountof generated code and the coding distortion for each merge candidate,coding information of less amount of generated code and less codingdistortion is determined. A merge index corresponding to the determinedcoding information is encoded as a flag merge_idx represented by asecond syntax pattern of a prediction block. The amount of generatedcode calculated in this process is preferably calculated by simulatingcoding processes. However, approximations to simplify calculations or arough estimate can also be applied.

On the other hand, in FIG. 14, in the coding information selection unit236 of the inter prediction information derivation unit 205 of themoving picture encoding device, a merge candidate corresponding to aprovided merge index is selected from merge candidates registered in themerge candidate list, and inter prediction information of the mergecandidate is provided to the motion compensation prediction unit 206,and stored in the coding information storing memory 210.

A bitstream of moving pictures outputted from the moving pictureencoding device according to the embodiments described above has aspecific data format so that the data stream can be decoded inaccordance with the coding method used in the embodiments. A movingpicture decoding device corresponding to the moving picture encodingdevice can decode the bitstream in this specific format.

In case that a wired or wireless network is used in order to exchangebitstreams between the moving picture encoding device and the movingpicture decoding device, a bitstream may be transformed into a dataformat appropriate to the manner of transmission on the communicationpath so as to be transmitted. In this case, a moving picturetransmission device and a moving picture receiver device are provided.The moving picture transmission device transforms a bitstream outputfrom the moving picture encoding device into encoded data in a dataformat appropriate to the manner of transmission via the communicationpath and transmits the encoded data to the network. The moving picturereceiver device receives encoded data from the network, reconstructs abitstream, and provides the bitstream to the moving picture decodingdevice.

The moving picture transmission device includes a memory that buffers abitstream output from the moving picture encoding device, a packetprocessing unit that packetizes the bitstream, a transmission unit thattransmits the packetized bitstream via a network. The moving picturereceiver device includes a receiving unit that receives a packetizedbitstream via a network, a memory that buffers the received bitstream,and a packet processing unit that processes a packet of the encoded dataso as to generate a bitstream, and provides the bitstream to the movingpicture decoding device.

It is needless to mention that the processes relating to encoding anddecoding described above can be implemented as a transmission device, astorage, and/or a receiver device using hardware. The process can alsobe implemented by firmware stored in a read only memory (ROM), a flashmemory, or the like, or by software of computers or the like. Thefirmware program or the software program can be stored in a recordingmedium readable by a computer or the like and provided, can be providedfrom a server via a wired or wireless network, or can be provided bydata broadcasting as terrestrial broadcasting or satellite digitalbroadcasting.

Given above is an explanation based on the embodiments. The embodimentsare intended to be illustrative only and it will be obvious to thoseskilled in the art that various modifications to constituting elementsand processes could be developed and that such modifications are alsowithin the scope of the present invention.

What is claimed is:
 1. A moving picture encoding device that partitionsa first block, which is obtained by partitioning each picture, into oneor more second blocks and encodes a moving picture using interprediction, comprising: a first prediction information derivation unitconfigured to perform a derivation process of one or more first interprediction information candidates from inter prediction information ofone or more third blocks in a proximity of the second block subject toencoding in a picture subject to encoding; a second predictioninformation derivation unit configured to perform a derivation processof a second inter prediction information candidate from inter predictioninformation of a fourth block at a position identical to or in aproximity of the second block subject to encoding in a picture differentfrom the picture subject to encoding; a candidate list construction unitconfigured to construct a prediction information candidate listcomprising a prediction information candidate to which, in case that thefirst inter prediction information candidate is derived, the derivedfirst inter prediction information candidate is added, and in case thatthe second inter prediction information candidate is derived, thederived second inter prediction information candidate is added,respectively; a selection unit configured to select a candidate of interprediction information to be used for the inter prediction of the secondblock subject to encoding from the one or more prediction informationcandidates in the prediction information candidate list, and configuredto determine an index indicating inter prediction information; and anencoding unit configured to encode the index indicating inter predictioninformation to be used for the inter prediction of the second blocksubject to encoding, wherein the first prediction information derivationunit performs the derivation process of the first inter predictioninformation candidate without referring to coding information of a fifthblock included in a block identical to the first block including thesecond block subject to encoding, and wherein, in a partition mode wherethe first block is partitioned into an upper block and a lower blockarranged vertically, in the ration 1:3, the second predictioninformation derivation unit performs the derivation process of a secondinter prediction information candidate on the basis of a reference indexby setting the value of the reference index to a default value, withoutreferring to coding information of the fifth block included in a blockidentical to the first block including the second block subject toencoding.
 2. A transmission device comprising: a packet processing unitconfigured to packetize a bitstream encoded by a moving picture encodingmethod that partitions a first block, which is obtained by partitioningeach picture, into one or more second blocks and encodes a movingpicture using inter prediction, so as to obtain coded data; and atransmission unit configured to transmit the packetized bitstream,wherein the moving picture encoding method includes: performing aderivation process of one or more first inter prediction informationcandidates from inter prediction information of one or more third blocksin a proximity of the second block subject to encoding in a picturesubject to encoding; performing a derivation process of a second interprediction information candidate from inter prediction information of afourth block at a position identical to or in a proximity of the secondblock subject to encoding in a picture different from the picturesubject to encoding; constructing a prediction information candidatelist comprising a prediction information candidate to which, in casethat the first inter prediction information candidate is derived, thederived first inter prediction information candidate is added, and incase that the second inter prediction information candidate is derived,the derived second inter prediction information candidate is added,respectively; selecting a candidate of inter prediction information tobe used for the inter prediction of the second block subject to encodingfrom the one or more prediction information candidates in the predictioninformation candidate list, and determining an index indicating interprediction information; and encoding the index indicating interprediction information to be used for the inter prediction of the secondblock subject to encoding, wherein the performing a derivation processof one or more first inter prediction information candidates performsthe derivation process of the first inter prediction informationcandidate without referring to coding information of a fifth blockincluded in a block identical to the first block including the secondblock subject to encoding, and wherein, in a partition mode where thefirst block is partitioned into an upper block and a lower blockarranged vertically, in the ration 1:3, the performing of the secondprediction information derivation performs the derivation process of asecond inter prediction information candidate on the basis of areference index by setting the value of the reference index to a defaultvalue, without referring to coding information of the fifth blockincluded in a block identical to the first block including the secondblock subject to encoding.
 3. A transmission method comprising:processing of a packet that packetizes a bitstream encoded by a movingpicture encoding method that partitions a first block, which is obtainedby partitioning each picture, into one or more second blocks and encodesa moving picture using inter prediction, so as to obtain coded data; andtransmitting the packetized bitstream, wherein the moving pictureencoding method includes: performing a derivation process of one or morefirst inter prediction information candidates from inter predictioninformation of one or more third blocks in a proximity of the secondblock subject to encoding in a picture subject to encoding; performing aderivation process of a second inter prediction information candidatefrom inter prediction information of a fourth block at a positionidentical to or in a proximity of the second block subject to encodingin a picture different from the picture subject to encoding;constructing a prediction information candidate list comprising aprediction information candidate to which, in case that the first interprediction information candidate is derived, the derived first interprediction information candidate is added, and in case that the secondinter prediction information candidate is derived, the derived secondinter prediction information candidate is added, respectively; selectinga candidate of inter prediction information to be used for the interprediction of the second block subject to encoding from the one or moreprediction information candidates in the prediction informationcandidate list, and determining an index indicating inter predictioninformation; and encoding the index indicating inter predictioninformation to be used for the inter prediction of the second blocksubject to encoding, wherein the performing a derivation process of oneor more first inter prediction information candidates performs thederivation process of the first inter prediction information candidatewithout referring to coding information of a fifth block included in ablock identical to the first block including the second block subject toencoding, and wherein, in a partition mode where the first block ispartitioned into an upper block and a lower block arranged vertically,in the ration 1:3, the performing of the second prediction informationderivation performs the derivation process of a second inter predictioninformation candidate on the basis of a reference index by setting thevalue of the reference index to a default value, without referring tocoding information of the fifth block included in a block identical tothe first block including the second block subject to encoding.